Teams with distributed leadership type have release liaisons listed
in governance repository's projects.yaml file instead of a single PTL.
This was not handled in the check_approval.py script so far.
Fixing this by synchronizing the script with releases repository's
tool/check_approval.py script's relevant part.
Change-Id: I2433113e1168b10ba03831b30b82e46f3ec1c72f
88208ffa0d