Update grunt-contrib-clean requirement from ^1.0.0 to ^2.0.0
Update grunt-contrib-clean requirement from ^1.0.0 to ^2.0.0

Updates the requirements on [grunt-contrib-clean](https://github.com/gruntjs/grunt-contrib-clean) to permit the latest version.
- [Release notes](https://github.com/gruntjs/grunt-contrib-clean/releases)
- [Changelog](https://github.com/gruntjs/grunt-contrib-clean/blob/master/CHANGELOG)
- [Commits](https://github.com/gruntjs/grunt-contrib-clean/compare/v1.0.0...v2.0.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
snide/sphinx_rtd_theme,snide/sphinx_rtd_theme,snide/sphinx_rtd_theme,snide/sphinx_rtd_theme