Revert "Add warning message if developer depends on undocumented behavior"

This reverts commit a5ce5c14.

The warning message is no longer necessary since the existing behavior
is preserved.

Bug: 361260253
Test: N/A
Flag: com.android.text.flags.typeface_redesign_readonly
Change-Id: I0594d661a021b72ec398cb888a96ba4d1fbf74d7