MM-52532: Fix golangci warnings for public module (#23918)

https://mattermost.atlassian.net/browse/MM-52532

```release-note
NONE
```

server/public/model/push_notification.go

@@ -70,8 +70,8 @@ type PushNotification struct {
 }
 
 func (pn *PushNotification) DeepCopy() *PushNotification {
-	copy := *pn
-	return &copy
+	pnCopy := *pn
+	return &pnCopy
 }
 
 func (pn *PushNotification) SetDeviceIdAndPlatform(deviceId string) {