remove no-op lock/unlock from Lock sub-classes

src/remote/codec.cpp

@@ -51,8 +51,6 @@ struct BreakTransport : TransportSender
     {
         throw epics::pvAccess::detail::connection_closed_exception("Break");
     }
-    virtual void lock() {}
-    virtual void unlock() {}
 };
 } // namespace
 
@@ -1427,9 +1425,6 @@ public:
         control->flush(true);
     }
 
-    void lock() {}
-    void unlock() {}
-
 private:
     PVField::shared_pointer _data;
 };