ci: Only upload artifacts on the main repo
ci: Only upload artifacts on the main repo

Local forks only have limited storage space and 2 builds seems to
exceed that space. So we stop uploading artifacts for builds on forks.

osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi