Bump bleach from 3.1.1 to 3.1.2

Bumps [bleach](https://github.com/mozilla/bleach) from 3.1.1 to 3.1.2.
- [Release notes](https://github.com/mozilla/bleach/releases)
- [Changelog](https://github.com/mozilla/bleach/blob/master/CHANGES)
- [Commits](mozilla/bleach@v3.1.1...v3.1.2)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

dev_requirements.txt

@@ -6,7 +6,7 @@ Automat==0.8.0
 Babel==2.7.0
 backcall==0.1.0
 bitstring==3.1.6
-bleach==3.1.1
+bleach==3.1.2
 certifi==2019.6.16
 chardet==3.0.4
 Click==7.0