Remove unused IME_INVISIBLE flag

This flag was never actually passed to the code paths that check it, so
it was effectively unused.

Flag: EXEMPT refactor
Bug: 357821404
Test: atest NavigationBarTest DefaultImeVisibilityApplierTest
  CommandQueueTest
Change-Id: Ic10a6dfce1e289f96a0beb7ed7edf25c39aa547b