fix(lint): refine standard-track exception handling

[caugner]

Summary

Fixes two issues noticed after merging #28810:

1. Stage changes to the exception list when running npm run lint:fix as part of the pre-commit hook. (Otherwise commits that fix spec URLs won't automatically include the update to the exception list.)
2. Decouple the test case from the exception list. (The unit test started failing both in Add more spec_urls; set some standard_tracks to false (APIs A-E) #27671 and Fix standard track exceptions #29223, because the tested feature is no longer in the list.)

Test results and supporting details

Related issues

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[LeoMcA]

Lgtm, one nit: