Revert "Roll engine to version b148e628ec86b3a9a0382e0bcfae73f0390a8232 (#20427)" (#20631)

Reason for revert: The package:flutter_gallery_assets has removed some images which are required for the examples/flutter_gallery, so the gallery build is failing (only discovered after landing, since gallery doesn't seem to get built during github PR presubmit checks)