Remove ime_switcher_revamp and _api flags

This removes the ime_switcher_revamp (from [1]) and
ime_switcher_revamp_api (from [2]) code paths and flags, as the flags
are now fully enabled and submitted.

  [1]: I1005cb6b10682f3e91a7ed847c290fcc206b5faa
  [2]: I336c1329c4159e9e9a7d4270cdb20c426a506b83

FCRS_CODE : mdem99fluaqbdr

Flag: EXEMPT flag removal
Bug: 281029564
Test: atest InputMethodInfoTest
  InputMethodMenuControllerTest
  InputMethodServiceTest
  InputMethodSubtypeSwitchingControllerTest
  InputMethodManagerTest
  InputMethodSubtypeTest
  TaskbarNavButtonControllerTest
Change-Id: I2c08e3f17abd09fa59df0648f65cb02c2e0194a2