Python: fix VariableWrite and remove unneded step

Author: yoff

Diff for: python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll

@@ -300,14 +300,6 @@ module LocalFlow {
       nodeTo.(CfgNode).getNode() = def.getDefiningNode()
     )
     or
-    // Assignment to captured variables
-    // These are not covered by the `AssignmentDefinition`s in the case above,
-    // as they are not necessarily live.
-    nodeFrom.(CfgNode).getNode() = nodeTo.(CfgNode).getNode().(DefinitionNode).getValue() and
-    nodeTo.asExpr() = any(VariableCapture::CapturedVariable c).getAStore() and
-    // Exclude assignments to parameters. These are from default values and not local.
-    not nodeTo instanceof ParameterNode
-    or
     // With definition
     //   `with f(42) as x:`
     //   nodeFrom is `f(42)`

Diff for: python/ql/lib/semmle/python/dataflow/new/internal/VariableCapture.qll

@@ -72,7 +72,7 @@ private module CaptureInput implements Shared::InputSig<Location> {
   class VariableWrite extends ControlFlowNode {
     CapturedVariable v;
 
-    VariableWrite() { this = v.getAStore().getAFlowNode() }
+    VariableWrite() { this = v.getAStore().getAFlowNode().(DefinitionNode).getValue() }
 
     CapturedVariable getVariable() { result = v }