The QT_OPENGL_ES* macros are leftovers from an earlier,
ad hoc configuration system, which has since been
replaced by QT_CONFIG. To clean things up in Qt 6,
we use the new way instead.
Task-number: QTBUG-83467
Change-Id: I578dc7695bff9d5ee303b22e44f60fee22fe0c28
Reviewed-by: Lars Knoll <lars.knoll@qt.io>