Remove unnecessary call to truncate() am: 8436f18976

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2320955

Change-Id: I8949b0c450231a517c2ff862a8b5bbb6822f9a4a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>