Data flow: Add stub expectsContent for all languages

java/ql/lib/semmle/code/java/dataflow/internal/DataFlowPrivate.qll

@@ -160,6 +160,12 @@ predicate clearsContent(Node n, Content c) {
   FlowSummaryImpl::Private::Steps::summaryClearsContent(n, c)
 }
 
+/**
+ * Holds if the value that is being tracked is expected to be stored inside content `c`
+ * at node `n`.
+ */
+predicate expectsContent(Node n, ContentSet c) { none() }
+
 /**
  * Gets a representative (boxed) type for `t` for the purpose of pruning
  * possible flow. A single type is used for all numeric types to account for