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>