The vendor image will have more than just proprietary modules in it
under Treble, so let's stop marking open source code as proprietary just
to move it to vendor.
Bug: 36452052
Bug: 37134596
Test: compare build.ninja before/after, no changes.
Test: Set vendor: true, ensure it works.
Change-Id: I44b0ec7007d0e311bdcbd44b238b1ef2d05cc6ff