Material: QMetaType::type(const char*) is deprecatred and shouldn't be used in new code

And it looks like that QMetaType::type("Base::Quantity") neither works with Qt5 nor with Qt6 because it returns 0 as id that means the type is unknown.

src/Mod/Material/App/MaterialPyImpl.cpp

@@ -350,7 +350,7 @@ static PyObject* _pyObjectFromVariant(const QVariant& value)
         return new PyObject();
     }
 
-    if (value.userType() == QMetaType::type("Base::Quantity")) {
+    if (value.userType() == qMetaTypeId<Base::Quantity>()) {
         return new Base::QuantityPy(new Base::Quantity(value.value<Base::Quantity>()));
     }
     else if (value.userType() == QMetaType::Double) {