Run full pipeline when feature flag is deleted

Run full end-to-end test suite when a feature flag is deleted. Ideally, we would want to run the full suite (or selectively the related e2e tests) when a feature flag is introduced (at least with the flag on). But currently, we only run ee:instance-parallel job to avoid overloading the runners. Until that is possible, this will provide some needed coverage such as in cases like these.