Fix Z-order after showing modal dialog in wxOSX

Explicitly bring the parent to top when hiding a modal dialog, this doesn't
seem to do any harm and it fixes a very annoying regression with bringing the
application frame, and not the dialog parent, if it's different, to the top of
Z-order after dismissing the dialog.

Closes #16204.

src/osx/dialog_osx.cpp

@@ -178,5 +178,9 @@ void wxDialog::EndModal(int retCode)
 
     SetReturnCode(retCode);
     Show(false);
+
+    // Prevent app frame from taking z-order precedence
+    if( GetParent() )
+        GetParent()->Raise();
 }