clarify pipeline group resources docs
clarify pipeline group resources docs

also moved reference to concourse pipeline up; otherwise it looks
related to resources docs

[#79704624]

sedouard/concourse,longnguyen11288/concourse,Amit-PivotalLabs/concourse,longnguyen11288/concourse,Amit-PivotalLabs/concourse,concourse/concourse,beni55/concourse,Amit-PivotalLabs/concourse,zachgersh/concourse,concourse/concourse,CloudCredo/concourse,cjcjameson/concourse,zachgersh/concourse,longnguyen11288/concourse,holgero/concourse,squeedee/concourse,CloudCredo/concourse,jbayer/concourse,holgero/concourse,beni55/concourse,concourse/concourse,jbayer/concourse,jbayer/concourse,holgero/concourse,zachgersh/concourse,sedouard/concourse,cjcjameson/concourse,cjcjameson/concourse,sedouard/concourse,concourse/concourse,concourse/concourse,squeedee/concourse,squeedee/concourse,beni55/concourse,CloudCredo/concourse