Remove very slow line in perf test.

This single line change brought the test from 140 triples/s
to 370,000 triples/s. Gotta find a way to optimize LSUP_graph_size()!

src/graph.c

@@ -357,7 +357,6 @@ LSUP_graph_add_txn (
             rc = db_rc;
             goto finally;
         }
-        log_trace ("Graph size at end of add iter: %lu", LSUP_graph_size (gr));
     }
 
 finally: