Bump axe-core from 3.5.3 to 3.5.4

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.683.0 to 2.687.0.
- [Release notes](https://github.com/aws/aws-sdk-js/releases)
- [Changelog](https://github.com/aws/aws-sdk-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-js/compare/v2.683.0...v2.687.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [axe-core](https://github.com/dequelabs/axe-core) from 3.5.3 to 3.5.4.
- [Release notes](https://github.com/dequelabs/axe-core/releases)
- [Changelog](https://github.com/dequelabs/axe-core/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/dequelabs/axe-core/compare/v3.5.3...v3.5.4)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Tidy/Organize existing SASS color variables

Standardize text colors

- Also tighten padding as it was a little loose

Add deprecation notice for IE11 browsers

Remove unused/unnecessary SASS vars and mixins

- Remove unnecessary clearfix in annotation-header. We don't use floats
  in the layout of annotation threads or annotations any more.

- Remove unused variables

- Remove an unused mixin in `forms.scss`

Rectify infinite load on single-annotation, stream views

Bump mocha from 7.1.2 to 7.2.0

Bump karma from 5.0.8 to 5.0.9

Bump terser from 4.6.13 to 4.7.0

Bump fetch-mock from 9.9.0 to 9.10.1

Bump preact from 10.4.1 to 10.4.4

Fix installing tox

Update 3 config keys

- `allowLeavingGroups`
- `groups` when used with “$rpc:requestGroups” value
- `requestConfigFromFrame`

Our scripting automatically installs tox in pyenv so you don't have to
install tox manually or system-wide. Unfortunately it wasn't working:
the installed tox doesn't appear on your PATH until you run a
`pyenv rehash`

Bump chance from 1.1.5 to 1.1.6

Remove `OAUTH_TOKENS_CHANGED` event

Remove unused diff-match-patch dependency

We don't use this package directly any more, although there is still a
transitive dependency on it via dom-anchor-text-quote.

Bumps [aws-sdk](https://github.com/aws/aws-sdk-js) from 2.679.0 to 2.683.0.
- [Release notes](https://github.com/aws/aws-sdk-js/releases)
- [Changelog](https://github.com/aws/aws-sdk-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-js/compare/v2.679.0...v2.683.0)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>