Remove an out-of-date comment

rts/Stats.c

@@ -564,8 +564,7 @@ stat_exit(int alloc)
 
         // heapCensus() is called by the GC, so RP and HC time are
         // included in the GC stats.  We therefore subtract them to
-        // obtain the actual GC cpu time.  XXX: we aren't doing this
-        // for elapsed time.
+        // obtain the actual GC cpu time.
         gc_cpu     -= 0 + PROF_VAL(RP_tot_time + HC_tot_time);
         gc_elapsed -= 0 + PROF_VAL(RPe_tot_time + HCe_tot_time);