Fix conflicting JavaDoc of TYPE_TEXT_FLAG_NO_SUGGESTIONS

TYPE_TEXT_FLAG_NO_SUGGESTIONS is just a hint and does not mean
IME should never show a UI to display suggestions.

This CL makes that point clear in JavaDoc.

Test: checkbuild
Bug: 35875399
Bug: 38139781
Bug: 38184682
Fixes: 65693181
Change-Id: Id0c3b6bc05689a5f1c8b52637664f59d45850a60