Cleanup non-stripped feature flag.

Unfortunately, we can't do actual logic in our feature flags (or they
don't get stripped out). This is somewhat important when we enable a
feature by default, as the `FEATURE.isEnabled` check does not get
stripped, but the `ENV` var is also likely not present, massive trolling
ensues.
Merge pull request #5028 from rjackson/fix-feature-flag

Cleanup non-stripped Query Params feature flag.