Remove space before a period

Author: MasterDuke17

doc/Language/concurrency.pod6

@@ -784,7 +784,7 @@ example, in this code:
     $slot = 'foo';
 
 The third line is the critical section as that is when the array is extended.
-The simplest fix is to use a L<Lock> to protect the critical section .  A
+The simplest fix is to use a L<Lock> to protect the critical section.  A
 possibly better fix would be to refactor the code so that sharing a container
 is not necessary.