update_engine: update op buf size with vabc_none am: 5f07b22b85

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2907335

Change-Id: I9be835238761f960628fea4d24546bb63c9ba8aa
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>