Change Typeface redesign flag to readonly

This redesign feature does not support runtime flag flip.
Therefore, need to be fixed flag.

Bug: 361260253
Bug: 377690190
Test: atest CtsWidgetTestCases
Test: atest CtsTextTestCases
Test: atest CtsGraphicsTestCases
Test: atest minikin_tests
Flag: com.android.text.flags.typeface_redesign_readonly
Change-Id: I19e18636907646db0b8a9b9db097478e2b61d149