Bump cornice from 5.1.0 to 5.2.0

Bumps [cornice](https://github.com/mozilla-services/cornice) from 5.1.0 to 5.2.0.
- [Release notes](https://github.com/mozilla-services/cornice/releases)
- [Changelog](https://github.com/Cornices/cornice/blob/master/CHANGES.txt)
- [Commits](Cornices/cornice@5.1.0...5.2.0)

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

requirements.txt

@@ -4,7 +4,7 @@ cffi==1.14.5
 chardet==4.0.0
 colander==1.8.3
 colorama==0.4.4
-cornice==5.1.0
+cornice==5.2.0
 cornice-swagger==1.0.0
 dockerflow==2020.10.0
 hupper==1.10.2