Remove banner that redirects users from Settings > CI/CD > Runner to the new Runners page

Details

Now that we have had the banner up that redirects users from the previous location of group runners (Settings > CI/CD > Runner) to the new location (CI/CD > Runners), for many milestones, we should consider removing it.

Proposal

We implemented this change in 15.0, and we could potentially remove it in 16.0. @DarrenEastman brought up a good point that this could be considered a deprecation as to make a final announcement of where the new group runners view is.