build(deps): bump fixtures from 4.1.0 to 4.2.2

Bumps [fixtures](https://github.com/testing-cabal/fixtures) from 4.1.0 to 4.2.2.
- [Changelog](https://github.com/testing-cabal/fixtures/blob/master/NEWS)
- [Commits](testing-cabal/fixtures@4.1.0...4.2.2)

---
updated-dependencies:
- dependency-name: fixtures
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -15,7 +15,7 @@ git+https://github.com/snarfed/oauth-dropins.git#egg=oauth_dropins
 git+https://github.com/dvska/gdata-python3.git#egg=gdata
 
 # required for mox3, not prod
-fixtures==4.1.0
+fixtures==4.2.2
 pbr==6.1.0
 
 async-timeout==5.0.1