Added extservices in apex_available for Permission flags

Suggested by the build, this is required while adding the Permission Flags dependency to external/libtextclassifier

Bug: 388898030
Test: pre-submit
Flag: android.permission.flags.enable_otp_in_text_classifiers
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:bdf2ba0a61fee1ee8c25504509de17bdde7d3fb3)
Merged-In: Id09876d49337ec884a7cb347720d2787f2c428be
Change-Id: Id09876d49337ec884a7cb347720d2787f2c428be
syncing changes from git_main to main