[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

@@ -2,4 +2,4 @@ openwisp-utils[qa,selenium] @ https://github.com/openwisp/openwisp-utils/tarball
 django-redis~=5.4.0
 mock-ssh-server~=0.9.0
 channels_redis~=4.1.0
-freezegun~=1.1.0
+freezegun~=1.5.1