Remove unnecessary loading of settings in update hook (#9496)

This PR simply makes update an empty command rather than needlessly load the settings for each reference.

cmd/hook.go

@@ -181,18 +181,7 @@ Gitea or set your environment appropriately.`, "")
 }
 
 func runHookUpdate(c *cli.Context) error {
- if len(os.Getenv("SSH_ORIGINAL_COMMAND")) == 0 {
- if setting.OnlyAllowPushIfGiteaEnvironmentSet {
- fail(`Rejecting changes as Gitea environment not set.
-If you are pushing over SSH you must push with a key managed by
-Gitea or set your environment appropriately.`, "")
- } else {
- return nil
- }
- }
-
- setup("hooks/update.log", false)
-
+ // Update is empty and is kept only for backwards compatibility
  return nil
 }