chore(deps): bump testfixtures from 6.18.4 to 6.18.5 (#187)

Bumps [testfixtures](https://github.com/Simplistix/testfixtures) from 6.18.4 to 6.18.5.
- [Release notes](https://github.com/Simplistix/testfixtures/releases)
- [Changelog](https://github.com/simplistix/testfixtures/blob/master/CHANGELOG.rst)
- [Commits](simplistix/testfixtures@6.18.4...6.18.5)

---
updated-dependencies:
- dependency-name: testfixtures
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]