Mark android.view.inputmethod.InputMethodInfoTest as @SmallTest

InputMethodInfoTest was originally introduced without any test size
annotation [1] then marked as @LargeTest in a large mechanical
cleanup.

This is why InputMethodInfoTest is currently marked as @LargeTest.

Anyway, most likely InputMethodInfoTest is a small set of tests hence
this CL does so.

 [1]: I0f6b130a7df57557e40b52a7b7ac00be965a17c3
      e12a6fff
 [2]: Ifd466251b92728f9bbfa3cbd8fd21d34490f4eb1
      bdbde555

Bug: 115894235
Test: atest FrameworksCoreTests:android.view.inputmethod.InputMethodInfoTest
Change-Id: I0aae1a6d7287e4343eece56565c75856b762d7fa