Remove redundant tests for IMM#isFullscreenMode()

The following APIs are already tested with
BaseInputConnectionTest#testReportFullscreenMode().

 * BaseInputConnection#reportFullscreenMode(boolean)
 * InputMethodManager#isFullscreenMode()

There is no need to test the same scenario in
InputMethodManagerTest#testInputMethodManager().

Bug: 72922405
Test: atest CtsInputMethodTestCases
Change-Id: I4dd924e0425f9c5bf1eb2e3dd2560e3da66a03be
1 file changed