Remove QObjectRef in favor of QPointer (#4666)

* replace usage of QObjectRef with QPointer

* delete QObjectRef class

* inlucde QPointer header

* Add changelog entry

* use isNull() instead of ! data()

---------

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/common/NetworkPrivate.hpp

@@ -1,10 +1,10 @@
 #pragma once
 
 #include "common/NetworkCommon.hpp"
-#include "util/QObjectRef.hpp"
 
 #include <QHttpMultiPart>
 #include <QNetworkRequest>
+#include <QPointer>
 #include <QTimer>
 
 #include <functional>
@@ -38,7 +38,7 @@ struct NetworkData {
 
     QNetworkRequest request_;
     bool hasCaller_{};
-    QObjectRef<QObject> caller_;
+    QPointer<QObject> caller_;
     bool cache_{};
     bool executeConcurrently_{};