Overapproximate CapturedVariablesArgumentNode

We just create one for each call, not just the ones that capture
variables.

Of course, this causes a _lot_ of nodes to be instances of
`CapturedVariablesArgumentNode`, which made the override of `toString`
problematic, so that was removed as well.

Author: tausbn

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

@@ -1725,14 +1725,7 @@ private class SummaryPostUpdateNode extends FlowSummaryNode, PostUpdateNodeImpl
 class CapturedVariablesArgumentNode extends CfgNode {
   CallNode callNode;
 
-  CapturedVariablesArgumentNode() {
-    node = callNode.getFunction() and
-    exists(Function target | resolveCall(callNode, target, _) |
-      target = any(VariableCapture::CapturedVariable v).getACapturingScope()
-    )
-  }
-
-  override string toString() { result = "Capturing closure argument" }
+  CapturedVariablesArgumentNode() { node = callNode.getFunction() }
 }
 
 class CapturedVariablesArgumentNodeAsArgumentNode extends CapturedVariablesArgumentNode,