ANDROID: android/OWNERS: drop gki-abi-approvers@

Group support is not implemented and this rather disturbes downstream
merges. So, drop them.

Fixes: 2fa0951b66b3 ("ANDROID: Initial Android 12 OWNERS for abi metafiles")
Signed-off-by: Matthias Maennich <maennich@google.com>
Change-Id: I7d1462ff87b05eb678b1c97f5e0b89b97d4e91a5