Fix overlapping text in headings in annotation bodies

Parent elements of annotation cards set line heights to absolute pixel
values. Annotation card headings then inherit this and as a result,
their line height is too small for the font size.

We ought to reconsider the way line heights are set elsewhere in the
app, but resetting the line height in the `styled-text` mixin ensures
that annotation body styles are protected from whatever the parent
elements do with it.

Add direct linked group to store

Add abililty to clear groups in store

- Fix minor mistake in filterGroups where directLinkedGroupId should be
set to null rather than undefined.

This is needed to be able to clear the group state when logging
out and logging in.

Use same direct-linked group error when logged-in

Get group for direct-linked ann in group service

- Fetches the direct-linked annotation's group when the direct-linked
  annotation's group is not fetched by the group.list, profile.group,
  or the direct-linked group.
- Simplify the logic in the filterGroups function and pass the
  direct-linked annotation's groupid to the filterGroups function to
  avoid a duplicate annotation fetch.
- Add tests.
This is a fix for hypothesis/product-backlog#986.

Upgrade mockable-imports Babel plugin and remove unused mock

There was a bug in previous versions of the plugin that allowed unused
mocks in certain cases.

Fix bug where direct linked group is duplicated

Do not add the direct-linked group to featuredGroups if it is already
present. This happens when a group is direct-linked to but the group
is already scoped to the page so the direct-linked group shows up twice.

Bump postcss from 7.0.14 to 7.0.16

Bump jquery from 3.4.0 to 3.4.1

Bump eslint-plugin-react from 7.12.4 to 7.13.0

Bump @octokit/rest from 16.25.0 to 16.25.2

Bump babel-plugin-istanbul from 5.1.3 to 5.1.4

Bumps [postcss](https://github.com/postcss/postcss) from 7.0.14 to 7.0.16.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/7.0.14...7.0.16)
Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [babel-plugin-istanbul](https://github.com/istanbuljs/babel-plugin-istanbul) from 5.1.3 to 5.1.4.
- [Release notes](https://github.com/istanbuljs/babel-plugin-istanbul/releases)
- [Changelog](https://github.com/istanbuljs/babel-plugin-istanbul/blob/master/CHANGELOG.md)
- [Commits](https://github.com/istanbuljs/babel-plugin-istanbul/compare/v5.1.3...v5.1.4)
Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [@octokit/rest](https://github.com/octokit/rest.js) from 16.25.0 to 16.25.2.
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](https://github.com/octokit/rest.js/compare/v16.25.0...v16.25.2)
Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [jquery](https://github.com/jquery/jquery) from 3.4.0 to 3.4.1.
- [Release notes](https://github.com/jquery/jquery/releases)
- [Commits](https://github.com/jquery/jquery/compare/3.4.0...3.4.1)
Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [eslint-plugin-react](https://github.com/yannickcr/eslint-plugin-react) from 7.12.4 to 7.13.0.
- [Release notes](https://github.com/yannickcr/eslint-plugin-react/releases)
- [Changelog](https://github.com/yannickcr/eslint-plugin-react/blob/master/CHANGELOG.md)
- [Commits](https://github.com/yannickcr/eslint-plugin-react/compare/v7.12.4...v7.13.0)
Signed-off-by: dependabot[bot] <support@dependabot.com>

Upgrade Preact

This fixes an issue with `Fragment`s containing a conditionally-rendered
last child.

Convert mocking to mockable imports (4/4)

Fix GitHub release generation script

Git has two types of tags, lightweight tags and annotated tags. Only
annotated tags have a "tag date" associated with them. Recently it
appears that releases have been tagged with lightweight tags rather than
annotated tags, which the `generate-change-list.js` script did not
handle.

 - When fetching the last tag, use the commit date as a fallback for the
   tag date, and bail with an error if no date can be found

 - Link to the HTML rather than JSON representation of a PR in release
   notes

 - Fix a warning about use of deprecated GitHub API pagination methods
   by switching to the pagination APIs described at
   https://octokit.github.io/rest.js/#pagination

 - Support running the `generate-change-list.js` script as a CLI tool
   for debugging using `node generate-change-list.js <tag name>`

 - Skip Dependabot PRs in the change list, as these add a lot of noise.
   Generally readers are going to be interested in non-maintenance PRs.

Even though the linked issue no longer applies, this module is never
used outside the sidebar app so there is no concern with it having
sidebar app-specific dependencies.

These are no longer used as all mocking is now done via the `$imports`
export added to modules by the mockable-imports Babel plugin.

This speeds up the test run by a few seconds as it eliminates an extra
parsing of the source.

Convert mocking to mockable imports (3/4)

This enables mocking of the `anchoring/html` module in tests without having
to patch the `anchoring` property after the class is constructed.

Convert mocking to mockable-imports (2/4)

Convert remaining uses of proxyquire to babel-plugin-mockable-imports,
except for modules written in CoffeeScript, as the Babel plugin needs an
update to support the way groups of `<var> = require(<module>)`
statements get compiled.

Bump @babel/preset-env from 7.4.3 to 7.4.4