C#: Add remote type source kind in model validation.

Author: JarLob

csharp/ql/lib/semmle/code/csharp/dataflow/ExternalFlow.qll

@@ -338,7 +338,7 @@ module ModelValidation {
     )
     or
     exists(string kind | sourceModel(_, _, _, _, _, _, _, kind, _) |
-      not kind = ["local", "file"] and
+      not kind = ["local", "remote", "file"] and
       result = "Invalid kind \"" + kind + "\" in source model."
     )
   }