Set min_sdk_version for com.android.extservices

Because codename "R" is not supported yet for android_app's
min_sdk_version, apex.min_sdk_version is set to "current" instead.

This should be set to 30 in AOSP after SDK finalization lands.

Bug: 152655956
Test: m
Change-Id: I5962c596ccd1d2dedb263f527b1a6dd062581b50