Don't use old style casts

Ref: https://github.com/qbittorrent/qBittorrent/runs/2996702005?check_suite_focus=true#step:8:298

src/gui/macutilities.mm

@@ -68,14 +68,14 @@ namespace MacUtils
 
         if (class_getInstanceMethod(delClass, shouldHandle))
         {
-            if (class_replaceMethod(delClass, shouldHandle, (IMP)dockClickHandler, "B@:"))
+            if (class_replaceMethod(delClass, shouldHandle, reinterpret_cast<IMP>(dockClickHandler), "B@:"))
                 qDebug("Registered dock click handler (replaced original method)");
             else
                 qWarning("Failed to replace method for dock click handler");
         }
         else
         {
-            if (class_addMethod(delClass, shouldHandle, (IMP)dockClickHandler, "B@:"))
+            if (class_addMethod(delClass, shouldHandle, reinterpret_cast<IMP>(dockClickHandler), "B@:"))
                 qDebug("Registered dock click handler");
             else
                 qWarning("Failed to register dock click handler");