Bump freezegun from 0.3.11 to 0.3.12 in /backend/uclapi
Bump freezegun from 0.3.11 to 0.3.12 in /backend/uclapi

Bumps [freezegun](https://github.com/spulec/freezegun) from 0.3.11 to 0.3.12.
- [Release notes](https://github.com/spulec/freezegun/releases)
- [Changelog](https://github.com/spulec/freezegun/blob/master/CHANGELOG)
- [Commits](https://github.com/spulec/freezegun/compare/0.3.11...0.3.12)
uclapi/uclapi,uclapi/uclapi,uclapi/uclapi,uclapi/uclapi