Set Gitlab::Shell#create_repository as OPT_OUT
Set Gitlab::Shell#create_repository as OPT_OUT

On .com repositories are created through Gitaly for a while now. For
customers this is not the case unless these have chosen to do so through
feature flags. By moving this to opt out, everyone will be using this.

This move is part of the migration issue
https://gitlab.com/gitlab-org/gitaly/issues/593

The bigger impact this commit will have is that tests that use a
repository through `FactoryBot.create(:project, :repository)` will now
use Gitaly to do so. As tests run on the same disk, or at least machine,
this will most probably slow them down.

axilleas/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,jirutka/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,jirutka/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,iiet/iiet-git,iiet/iiet-git