Python dependency: Bump fixtures from 4.2.8 to 4.3.0 in /web/regression

Bumps [fixtures](https://github.com/testing-cabal/fixtures) from 4.2.8 to 4.3.0.
- [Changelog](https://github.com/testing-cabal/fixtures/blob/master/NEWS)
- [Commits](testing-cabal/fixtures@4.2.8...4.3.0)

---
updated-dependencies:
- dependency-name: fixtures
  dependency-version: 4.3.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

web/regression/requirements.txt

@@ -22,7 +22,7 @@
 # relevant packages.
 ###########################################################
 extras==1.0.0
-fixtures==4.2.8
+fixtures==4.3.0
 linecache2==1.0.0
 pbr==7.0.3
 pycodestyle>=2.5.0