Remove red-ventures as known code_owner_squad

[robrap]

This is a clean-up task for the addition of red-ventures to the DD monitor LMS unrecognized code_owner_squad.

• This clean-up is blocked until red-ventures has been removed from edx-internals (i.e. this search of edx-internals no longer shows results).
• See relevant Slack thread for moving code_owner_squad value to a 2U team.

[robrap]

Blocked on fix from Marketplace. Last discussed on Sept 30, 2024. Let's check in on this mid-to-leat October.

[robrap]

Completed this, and updated the runbook and alerting as well.