[deps] Update freezegun requirement from ~=1.1.0 to ~=1.5.1

Updates the requirements on [freezegun](https://github.com/spulec/freezegun) to permit the latest version.
- [Release notes](https://github.com/spulec/freezegun/releases)
- [Changelog](https://github.com/spulec/freezegun/blob/master/CHANGELOG)
- [Commits](spulec/freezegun@1.1.0...1.5.1)

---
updated-dependencies:
- dependency-name: freezegun
  dependency-type: direct:production
...

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

requirements-test.txt

@@ -1,7 +1,7 @@
 responses~=0.25.3
 pytest-asyncio~=0.23.7
 pytest-django~=4.8.0
-freezegun~=1.1.0
+freezegun~=1.5.1
 # Needed to test integrations
 openwisp-monitoring @ https://github.com/openwisp/openwisp-monitoring/tarball/master
 openwisp-controller @ https://github.com/openwisp/openwisp-controller/tarball/master