Bump requests-mock from 1.9.3 to 1.12.1 in /requirements

Bumps [requests-mock](https://github.com/jamielennox/requests-mock) from 1.9.3 to 1.12.1.
- [Release notes](https://github.com/jamielennox/requests-mock/releases)
- [Commits](jamielennox/requests-mock@1.9.3...1.12.1)

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

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

requirements/tests.txt

@@ -1,4 +1,4 @@
 -r dev.txt
 coverage==6.3.2
-requests-mock==1.9.3
+requests-mock==1.12.1
 tox<5.0.0