Modify AT_LEAST_S check to include SDK int

BuildCompat.isAtLeastS() in Launcher dependency only checks if the
code name is "S". In the recent version of Android, the code name has
changed to "REL".

Test: Open Widgets picker, expand Conversations and observe a preview
      layout is shown.
Fix: 191239040, 191216821
Change-Id: I6a6e647d4cb327d251bde3484ea2d2e79c0f86f5