Bump bleach from 2.1.3 to 3.1.2

Bumps [bleach](https://github.com/mozilla/bleach) from 2.1.3 to 3.1.2.
- [Release notes](https://github.com/mozilla/bleach/releases)
- [Changelog](https://github.com/mozilla/bleach/blob/master/CHANGES)
- [Commits](mozilla/bleach@v2.1.3...v3.1.2)

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Author: dependabot[bot]