Add janitors to the OWNERS file am: e6072a5095 am: 58ca9212b4

Original change: https://android-review.googlesource.com/c/platform/external/libbackup/+/3423618

Change-Id: Ieca81946d4b083569d42972548e96c11f33ec169
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>