Code monitors: enable repo-aware monitors by default

Created by: camdencheek

This enables the cc-repo-aware-monitors flag by default if it is not set. This will make it so when customers update, they will be using repo-aware monitors. I intend to leave the feature flag in place until after the release cut so we have an emergency escape hatch, but I don't expect we'll need it.

Test plan

This has been enabled on sourcegraph.com for weeks. We should be good.