remove random generated name hack

We no longer need the random id hack for generating Cloud Run resource names as the provider now supports an autogenerate_revision_name flag which allows Google to generate the appropriate resource name for us.

Tested with the card database development instance by alternately re-deploying the development environment from the GitLab UI and then changing the max_scale parameter of the service. Previously attempting to modify a service once GitLab had deployed to it caused an error about name re-use. This is no longer the case with this MR applied.

Note: deployments making use of this will have to use a Google provider version > 3.16 and so a minimum provider version has been specified for the module. I'll prepare a related MR for the boilerplate although terraform init should be clever enough to install the Right Thing (TM) without changing existing deployments.

Closes #4 (closed)