Drawing: [skip ci] Fix several clazy issues:

* Missing reference in range-for with non trivial type [-Wclazy-range-loop-reference]
* Don't call QList::operator[]() on temporary [-Wclazy-detaching-temporary]
* Use multi-arg instead [-Wclazy-qstring-arg]

src/Mod/Drawing/App/AppDrawingPy.cpp

@@ -59,7 +59,7 @@ namespace Drawing {
     string key;
     string value;
 
-    for (auto keyPy : sourceRange.keys()) {
+    for (const auto& keyPy : sourceRange.keys()) {
       key = Py::String(keyPy);
       value = Py::String(sourceRange[keyPy]);
       *targetIt = {key, value};