Add janitors to the OWNERS file am: e6072a5095

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

Change-Id: I4c2d27367368d9cec20650906464fc3e83dc153a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>