Bump bleach from 3.1.0 to 3.1.2 in /demo/robotlab

Bumps [bleach](https://github.com/mozilla/bleach) from 3.1.0 to 3.1.2.
- [Release notes](https://github.com/mozilla/bleach/releases)
- [Changelog](https://github.com/mozilla/bleach/blob/master/CHANGES)
- [Commits](mozilla/bleach@v3.1.0...v3.1.2)

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

demo/robotlab/requirements-python3.txt

@@ -5,7 +5,7 @@ RESTinstance==1.0.0
 Send2Trash==1.5.0
 attrs==19.1.0
 backcall==0.1.0
-bleach==3.1.0
+bleach==3.1.2
 certifi==2019.6.16
 chardet==3.0.4
 click==7.0