Remove `ci_fix_input_types` feature flag

What does this MR do and why?

Note: This MR should not be merged until after the Summit PCL.

This flag is now fully rolled out and ready for removal. The new code introduced under the flag caused one regression involving boolean values given to CI variables. That regression was fixed by allowing variables to have boolean values, and no further regressions have arisen.

Changelog: fixed

Issue: #443302 (closed)