Fix docs for "adb push --sync" to better match the implementation. am: b683bd657c

Original change: https://android-review.googlesource.com/c/platform/packages/modules/adb/+/2976891

Change-Id: Icace98b2a104d3318ab0533125cb9bb83d93bc8c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>