Revert "Add OWNERS block to facilitate in migration"

This reverts commit 9e569671.

Reason for revert: atoms and associated protos have been migrated.  Removing migration block.

Merged-In: Ia1e4a73001ebc9509b8550c7957135172ce8938d
BUG: 167962588
Test: TH
Change-Id: I7a451021461a24c2788411f2028e8ffed73667e9
Exempt-From-Owner-Approval: Cleanup CL