Remove obsoleted functions from Utils::Gui namespace

`widget` parameter is kept for now to avoid major disruption for other PR.
Also add comments for loading svg images.

PR #16613.

src/gui/aboutdialog.cpp

@@ -113,7 +113,7 @@ AboutDialog::AboutDialog(QWidget *parent)
                                      "The database is licensed under the Creative Commons Attribution 4.0 International License"));
     m_ui->labelDBIP->setText(DBIPText);
 
-    Utils::Gui::resize(this, m_storeDialogSize);
+    resize(m_storeDialogSize);
     show();
 }