Remove the tested architectures from the README
Remove the tested architectures from the README

The list of tested architecture is difficult to maintain exhaustive and
up to date. It ends up being confusing.

HubLot/PBxplore,pierrepo/PBxplore,jbarnoud/PBxplore,pierrepo/PBxplore,jbarnoud/PBxplore,HubLot/PBxplore