zuul: move rubocop jobs to experimental

The rubocop (ruby style checkers) jobs are far from being ready to be
triggered on all patchset proposed.

Move rubocop jobs to the experimental pipeline
Comment them out from the other pipelines
Remove occurences of such jobs in the 'check' pipeline since that is run
for everyone.

Bug: 69245
Change-Id: I32439934bf48c55b74bb728fa9c92346507fc184