Remove the "app" label from policy server Deployment

[jvanz]

          Okay, an update after the daily call with the @kubewarden/kubewarden-developers. We've decided to hold off on this for now. We plan to revisit the [policy lifecycle](https://github.com/kubewarden/kubewarden-controller/issues/1019) in future releases, which will be a major breaking change, and we'll use that opportunity to remove the old "app" label from the deployment. Consequently, I'll close this PR and open a new one that keeps the "app" label alongside all the other changes, adding the standard label to the resources and the deployment.

Originally posted by @jvanz in #1084 (comment)