Python: Remove explicit jumpStep for default parameter values

tests added in #5238
functionality added in #6640

Author: RasmusWL

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

@@ -576,9 +576,6 @@ predicate jumpStepSharedWithTypeTracker(Node nodeFrom, Node nodeTo) {
       r.getAttributeName(), nodeFrom) and
     nodeTo = r
   )
-  or
-  // Default value for parameter flows to that parameter
-  defaultValueFlowStep(nodeFrom, nodeTo)
 }
 
 /**
@@ -799,19 +796,6 @@ predicate attributeStoreStep(Node nodeFrom, AttributeContent c, PostUpdateNode n
   )
 }
 
-predicate defaultValueFlowStep(CfgNode nodeFrom, CfgNode nodeTo) {
-  exists(Function f, Parameter p, ParameterDefinition def |
-    // `getArgByName` supports, unlike `getAnArg`, keyword-only parameters
-    p = f.getArgByName(_) and
-    nodeFrom.asExpr() = p.getDefault() and
-    // The following expresses
-    // nodeTo.(ParameterNode).getParameter() = p
-    // without non-monotonic recursion
-    def.getParameter() = p and
-    nodeTo.getNode() = def.getDefiningNode()
-  )
-}
-
 /**
  * Holds if data can flow from `nodeFrom` to `nodeTo` via a read of content `c`.
  */