Update usage of FontCollection::getSupportedTags().

Replace getSupportedTags() with getSupportedAxesCount() /
getSupportedAxisAt(), following minikin change.

Bug: 174672300
Test: atest CtsGraphicsTestCases:android.graphics.cts.TypefaceTest
Change-Id: I7959ea903cc73e89589d5f8bb5b5e5900ba6d5db