Code monitors: remove `repo:` filter requirement for code monitor queries

Created by: camdencheek

Closes #31943 (closed) Closes #31941 (closed)

This removes the repo: filter requirement for code monitors everywhere except on sourcegraph.com. I think it's best to keep in place on sourcegraph.com because it's a bit too easy to accidentally create a code monitor that hits every repo on sourcegraph.com, which will cause unnecessary load.

Test plan

Tested behavior with sg start and sg start dotcom

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