services/backup/OWNERS: Sync with internal version.

https://r.android.com/950439 and http://ag/7949925 already attempted
this, but a whitespace difference remained.

This CL copies ('cp') the internal file to AOSP master; the Merged-In line
refers to the internal CL that added the extra empty line, which should
lead to automerger skipping this CL when merging into branches that have
the other CL.

Bug: 129861520
Bug: 159055442
Test: Treehugger

Change-Id: I3f83e223a1c7d812f74515008e4c6005ebc3dbe2
Merged-In: I42c27dfc0f3f792c46fe60e0f6807e51a2c3f21e