v0.0.0-5091-gdbed734e7

Remove unnecessary flag library accidentally added earlier.

It was added in an initial version of
https://github.com/google/xls/commit/4bdbc9e44ee8d1d321c847bfedfe24d0960eeaeb ,
but was not needed anymore once finished.

PiperOrigin-RevId: 633355681