feat(gcloud): allow pinning gcloud cli version

[TheKevJames]

Summary

Hotfix for https://dialpad.slack.com/archives/C032J2L17KQ/p1646846366298429

Checklist

• [x] My comments/docstrings/type hints are clear
• [x] I've written new tests or this change does not need them
• [x] I've tested this manually
  • https://app.circleci.com/pipelines/github/talkiq/realtime-nlp/8006/workflows/a5dc901b-de3e-4ce4-8aba-df743a452917
• [x] The architecture diagrams have been updated, if need be
• [x] I've included any special rollback strategies above
• [x] Any relevant metrics/monitors/SLOs have been added or modified
• [x] I've notified all relevant stakeholders of the change
• [x] I've updated .github/CODEOWNERS, if relevant

[TheKevJames]

Yeah, I'd really rather have come up with something a bit less brittle, but I couldn't think of much else to dig into that script. Here's hoping the script remains mostly unchanged for a long time.