Bump pbr from 4.0.3 to 4.0.4 in /backend/uclapi
Bump pbr from 4.0.3 to 4.0.4 in /backend/uclapi

Bumps [pbr](https://docs.openstack.org/pbr/latest/) from 4.0.3 to 4.0.4.

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
uclapi/uclapi,uclapi/uclapi,uclapi/uclapi,uclapi/uclapi