Update mock requirement from <5.0.0 to <6.0.0

Updates the requirements on [mock](https://github.com/testing-cabal/mock) to permit the latest version.
- [Release notes](https://github.com/testing-cabal/mock/releases)
- [Changelog](https://github.com/testing-cabal/mock/blob/master/CHANGELOG.rst)
- [Commits](testing-cabal/mock@release-0.5.0...5.0.0)

---
updated-dependencies:
- dependency-name: mock
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -119,7 +119,7 @@ python-memcached<=1.59
 xmltodict<0.12.1
 inflection==0.3.1
 jdcal==1.4.1
-mock<5.0.0
+mock<6.0.0
 python-dateutil==2.8.1
 pytz==2020.4
 requests==2.25.1