chore(librarian): specify all generated files in remove_regex

[parthea]

This PR resolves the following issue when running librarian generate. Librarian now prevents generated files from clobbering existing files. All generated files must match remove_regex otherwise we will see errors like file existed in destination

time=2025-11-06T20:18:57.185Z level=INFO msg="=== Docker end ================================================================="
time=2025-11-06T20:18:57.185Z level=INFO msg="cleaning directories" "source roots"=[.]
time=2025-11-06T20:18:57.200Z level=INFO msg="copying library files" id=google-cloud-pubsub destination=/usr/local/google/home/partheniou/git/python-pubsub source=/tmp/librarian-2318048050/output/google-cloud-pubsub
time=2025-11-06T20:18:57.201Z level=ERROR msg="failed to generate library" id=google-cloud-pubsub err="file existed in destination: /usr/local/google/home/partheniou/git/python-pubsub/.coveragerc"
time=2025-11-06T20:18:57.201Z level=INFO msg="generation statistics" all=1 successes=0 skipped=0 failures=1
time=2025-11-06T20:18:57.201Z level=ERROR msg="librarian command failed" err="all 1 libraries failed to generate (skipped: 0)"

Command used

librarian generate --generate-unchanged