Python: Hide ModuleVariableNode in data-flow paths

They just add an extra step, and don't actually contribute any good
information for end-users.

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll

@@ -928,6 +928,8 @@ predicate forceHighPrecision(Content c) { none() }
 
 /** Holds if `n` should be hidden from path explanations. */
 predicate nodeIsHidden(Node n) {
+  n instanceof ModuleVariableNode
+  or
   n instanceof SummaryNode
   or
   n instanceof SummaryParameterNode