The gen_patch_test_tags.sh script was introduced as part of SERVER-57778 for --alias=query patch builds. It early exits when the build variant's name doesn't contain "query-patch-only". The determine_patch_tests Evergreen task which runs this script is not assigned to run on "Query Patch Only" build variants and therefore is always a no-op.

There were problems with the strategy of only running recently failed tests for --alias=query patch builds where they had a higher likelihood of merged changes being more often reverted. We can remove this functionality.