Flag cleanup: Remove check of AAPM MTE flag

As the android.security.aapm_feature_memory_tagging_extension flag is
removed (since it's been launched), remove the annotation requiring it
in the test.

Bug: 423961722
Test: atest CtsSecurityTestCases:android.security.cts.advancedprotection.MemoryTaggingExtensionTest
Flag: EXEMPT removing android.security.aapm_feature_memory_tagging_extension
Change-Id: If0b708e59b070bc13af4c7141b7f2627e29eea0f