cleanup some unused code and minor refactors (#1274)

Co-authored-by: Yusuke Kuoka <[email protected]>

controllers/horizontal_runner_autoscaler_webhook_on_push.go

@@ -15,10 +15,6 @@ func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) MatchPushEvent(event
 
 		push := g.Push
 
-		if push == nil {
-			return false
-		}
-
-		return true
+		return push != nil
 	}
 }