Dataflow: Address comments.

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll

@@ -712,7 +712,7 @@ predicate clearsContent(Node n, Content c) {
 
 private newtype TDataFlowType =
   TTodoDataFlowType() or
-  TTodoDataFlowType2()
+  TTodoDataFlowType2() // Add a dummy value to prevent bad functionality-induced joins arising from a type of size 1.
 
 class DataFlowType extends TDataFlowType {
   string toString() { result = "" }