Bump time-machine from 2.5.0 to 2.6.0

Bumps [time-machine](https://github.com/adamchainz/time-machine) from 2.5.0 to 2.6.0.
- [Release notes](https://github.com/adamchainz/time-machine/releases)
- [Changelog](https://github.com/adamchainz/time-machine/blob/main/HISTORY.rst)
- [Commits](https://github.com/adamchainz/time-machine/compare/2.5.0...2.6.0)

---
updated-dependencies:
- dependency-name: time-machine
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

requirements-dev.txt

@@ -14,7 +14,7 @@ pytest-mock==3.6.1
 pytest-random-order==1.0.4
 isort==5.10.1
 # For datetime mocking
-time-machine==2.5.0
+time-machine==2.6.0
 
 # Convert jupyter notebooks to markdown documents
 nbconvert==6.4.0