[deps] Bump freezegun from 1.5.1 to 1.5.4

Bumps [freezegun](https://github.com/spulec/freezegun) from 1.5.1 to 1.5.4.
- [Release notes](https://github.com/spulec/freezegun/releases)
- [Changelog](https://github.com/spulec/freezegun/blob/master/CHANGELOG)
- [Commits](spulec/freezegun@1.5.1...1.5.4)

---
updated-dependencies:
- dependency-name: freezegun
  dependency-version: 1.5.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

requirements-test.txt

@@ -2,4 +2,4 @@ nose2[coverage_plugin]>=0.6.5
 responses~=0.25.7
 openwisp-utils[qa] @ https://github.com/openwisp/openwisp-utils/tarball/1.2
 parameterized~=0.9.0
-freezegun==1.5.1
+freezegun==1.5.4