C++: Don't mention deprecated class

The language tests were failing because they don't tolerate mentioning a
deprecated class anywhere.

Author: jbj

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll

@@ -303,10 +303,12 @@ ParameterNode parameterNode(Parameter p) { result.getParameter() = p }
 VariableNode variableNode(Variable v) { result.getVariable() = v }
 
 /**
+ * DEPRECATED: See UninitializedNode.
+ *
  * Gets the `Node` corresponding to the value of an uninitialized local
  * variable `v`.
  */
-UninitializedNode uninitializedNode(LocalVariable v) { result.getLocalVariable() = v }
+Node uninitializedNode(LocalVariable v) { none() }
 
 /**
  * Holds if data flows from `nodeFrom` to `nodeTo` in exactly one local