Stop squad/theme mismatch issues in ownership spreadsheet

[robrap]

It is an annoyance to on-call, and to anyone updating the spreadsheet, to have to ensure that the theme stays in sync with the squad across all rows and sheets. This ticket would be for having an automated solution.

Some of the annoyance includes:

• Issues cause a pair of failures and alerts to deal with the same problem:
  • Build failed in Jenkins: OwnershipSync » edx-platform-code-owner-stage-prod-pr Ownership transfer: ReadTheDocs #399
  • Build failed in Jenkins: OwnershipSync » edx-platform-code-owner-edge-pr #1042
• I feel compelled to send reminders to the people making the changes to see if it helps keep the problem from happening again.