codeintel: ignore blocked repos from dirty commit graph age

Created by: Strum355

Skips blocked repositories with a dirty commit graph. Ideally these repos shouldnt be able to have any uploads (failing at an earlier stage), what Im assuming happened is that the repo became blocked between the upload being processed and the commit graph updater running for the repository (not sure how).

Closes https://github.com/sourcegraph/sourcegraph/issues/37996

Test plan

Only affects a single metrics counter