Language/Concurrency: fix punctuation

Author: taboege

doc/Language/concurrency.pod6

@@ -758,7 +758,7 @@ execution before normal completion:
      $cancellation.cancel;
      sleep 10;
 
-should only output 0 to 5,
+should only output 0 to 5.
 
 Despite the apparent advantage the L<Scheduler|/type/Scheduler> interface provides over
 that of L<Thread|/type/Thread> all of functionality is available through higher level