Bump bleach from 3.1.1 to 3.1.4

Bumps [bleach](https://github.com/mozilla/bleach) from 3.1.1 to 3.1.4.
- [Release notes](https://github.com/mozilla/bleach/releases)
- [Changelog](https://github.com/mozilla/bleach/blob/master/CHANGES)
- [Commits](mozilla/bleach@v3.1.1...v3.1.4)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1,4 +1,4 @@
-bleach==3.1.1
+bleach==3.1.4
 certifi==2020.6.20
 cffi==1.14.0
 cryptography==2.8