Fix API doc of TextSnapshot#getCursorCapsMode()

This is a follow up CL to my previous CL [1], which introduced
android.view.inputmethod.TextSnapshot.

There were typos in TextSnapshot#getCursorCapsMode() API document.
This CL just fixes them.

 [1]: I8e00dacce5ca915e276fdd8288ffc9167eb01a26
      dae47962

Bug: 205738567
Test: presubmit
Change-Id: I9ad0770ffb3fa8ffcdda09fbace6d654d8c4ee1e