Python: Fix missing global variable source nodes

In lieu of removing the offending flow (which would likely have
consequences for a lot of other tests), I opted to simply _include_
the relevant nodes directly.

python/ql/test/experimental/dataflow/ApiGraphs/test.py

@@ -72,7 +72,7 @@ def f():
     sink(foo) #$ use=moduleImport("danger").getMember("SOURCE")
     foo = NONSOURCE
     change_foo()
-    sink(foo) #$ MISSING: use=moduleImport("danger").getMember("SOURCE")
+    sink(foo) #$ use=moduleImport("danger").getMember("SOURCE")
 
 # Star imports