Remove references to the pdk product variable am: 6a40fabbdf

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2693293

Change-Id: I022ab1e7f4ea0275e0adb1d2e3b3a1586d77ac65
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>