Re-enable testShowHideSelf

In [1] we disabled this test while the insets refactor flag was enabled,
as this caused the show/hide flags to no longer be passed and checked.

However, we should still keep the main logic of the code for
requestShowSelf and requestHideSelf when no flags are used.

  [1]: Ia9e3b102a51f7635539a5af84e83d2fa76832359

Flag: EXEMPT testfix
Bug: 394079410
Test: atest InputMethodServiceTest#testShowHideSelf
Change-Id: Id193d05ff72fa8e318a88a5127b3cead022f28e7