We currently mark some labels with the platform bit.
This bit is used in some places for reporting the the canonical platform of devices.

Example:
goldeneye: https://cs.corp.google.com/piper///depot/google3/java/com/google/chrome/crosbuilds/common/data/entities/autotest/TkoTest.java?rcl=173483824&l=169

wmatrix:
https://cs.corp.google.com/chromeos_public/src/third_party/whining/src/backend/update_wmdb.py

afaict, the platform bit is either with a board:XXX label, or a variant:XXX label so far. This bit is not consistently set, and we want to drop it in skylab.

So, remove the dependencies (explicitly use model labels there) and delete the platform bit support from our autotest.