Upgrade libprotobuf-mutator to dbe588bfb6922060e557fe5b8ee27d2923000c1a am: 2fcbc34326

Original change: https://android-review.googlesource.com/c/platform/external/libprotobuf-mutator/+/2262286

Change-Id: I13e0551daf1b339ccb888684eb6b4f7b98d2f6f0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>