Update mock requirement from <5.0.0 to <6.0.0 in /.github/scripts (#495)

Updates the requirements on [mock](https://github.com/testing-cabal/mock) to permit the latest version.
- [Changelog](https://github.com/testing-cabal/mock/blob/master/CHANGELOG.rst)
- [Commits](testing-cabal/mock@release-0.5.0...5.1.0)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/scripts/requirements.txt

@@ -10,4 +10,4 @@ termcolor <2.5.0
 hypothesis <6.100.0
 python-Levenshtein <0.20.9 ; python_version == '2.7'
 levenshtein <=0.25.0 ; python_version >= '3.5'
-mock <5.0.0
+mock <6.0.0