Fixup of dataflow implementation.

Author: michaelnebel

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

@@ -610,6 +610,10 @@ module LocalFlow {
           or
           exists(Switch sw | sw.getACase() = cfe and sw.getExpr() = e1 and scope = sw)
         )
+        or
+        e1 = e2.(InterpolatedStringExpr).getAnInsert() and
+        scope = e2 and
+        isSuccessor = true
       )
     }