Update max API level for BC features to 27.

When this code was written, API level 27 wasn't public, so the limit
was set at 26.  Update it to 27 now that it's public.

Test: cts -m CtsLibcoreTestCases
Bug: 74612138
Change-Id: I3f1d17aa6cba30658db3d016a9dc74639c97f8a2
1 file changed