Delete PatchService and spec

What does this MR do and why?

Per Remove clusters_applications_* code (#366573 - closed) we are removing code around Clusters::Applications.

This MR

• Writes a deprecation note in ClusterPatchAppWorker.

• Noops the perform method for the ClusterPatchAppWorker.

• Deletes the Clusters::Applications::PatchService as it is only invoked by ClusterPatchAppWorker but this MR removes that invocation, leaving it unused.

• Deletes the Clusters::Applications::UpdateService as all it does is invoke the ClusterPatchAppWorker, which now does nothing.

• Deletes the unit specs for the service classes (I couldn't find a unit spec for the Worker class)

NOTE: on this branch no invocations found for the Clusters::Applications::UpdateService

➜  gitlab git:(hustewart-cluster-patch-app-worker) Rg UpdateService --files-with-matches -g '**/clusters/applications/**' -w
Rg UpdateService --files-with-matches -g '**/clusters/applications/**' -w
➜  gitlab git:(hustewart-cluster-patch-app-worker) Rg Clusters::Applications::UpdateService --files-with-matches
Rg Clusters::Applications::UpdateService --files-with-matches

and no invocations found for Clusters::Applications::PatchService

➜  gitlab git:(hustewart-cluster-patch-app-worker) Rg Clusters::Applications::PatchService --files-with-matches
Rg Clusters::Applications::PatchService --files-with-matches
➜  gitlab git:(hustewart-cluster-patch-app-worker) Rg PatchService --files-with-matches -g '**/clusters/applications/**' -w
Rg PatchService --files-with-matches -g '**/clusters/applications/**' -w
➜  gitlab git:(hustewart-cluster-patch-app-worker)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.