Remove assertion when database compaction finishes

Because the task status is updated only if the time elapsed
since the last task status update is greater than some treshold,
the value of the changes_done property might be smaller than
TotalChanges.

Closes COUCHDB-1451

src/couchdb/couch_db_updater.erl

@@ -954,7 +954,6 @@ copy_compact(Db, NewDb0, Retry) ->
             [{start_key, NewDb#db.update_seq + 1}]),
 
     NewDb3 = copy_docs(Db, NewDb2, lists:reverse(Uncopied), Retry),
-    TotalChanges = couch_task_status:get(changes_done),
 
     % copy misc header values
     if NewDb3#db.security /= Db#db.security ->