Fix an unused variable warning in deserialization.

Author: nadavrot

lib/Serialization/Deserialization.cpp

@@ -3955,6 +3955,7 @@ void ModuleFile::finishNormalConformance(NormalProtocolConformance *conformance,
   SmallVector<uint64_t, 16> scratch;
 
   unsigned kind = DeclTypeCursor.readRecord(entry.ID, scratch);
+  (void) kind;
   assert(kind == NORMAL_PROTOCOL_CONFORMANCE &&
          "registered lazy loader incorrectly");
   NormalProtocolConformanceLayout::readRecord(scratch, protoID,