Remove unused log member from dfcc_is_freeablet

We have a message handler that is initialised, the messaget member was
just some left-over.

Author: tautschnig

src/goto-instrument/contracts/dynamic-frames/dfcc_is_freeable.h

@@ -51,7 +51,6 @@ class dfcc_is_freeablet
 protected:
   dfcc_libraryt &library;
   message_handlert &message_handler;
-  messaget log;
 };
 
 #endif