Cleanup: Remove unused log_cmdq_key

There was an intention to add a CommandQueue in
mysql/mysql-server@eca5b0fc17a5bd6d4833d35a0d08c8549dd3b5ec
but it never appeared in any release (not even MySQL 5.7.3
where that commit appeared).

storage/innobase/handler/ha_innodb.cc

@@ -527,7 +527,6 @@ mysql_pfs_key_t	ibuf_bitmap_mutex_key;
 mysql_pfs_key_t	ibuf_mutex_key;
 mysql_pfs_key_t	ibuf_pessimistic_insert_mutex_key;
 mysql_pfs_key_t	log_sys_mutex_key;
-mysql_pfs_key_t	log_cmdq_mutex_key;
 mysql_pfs_key_t	log_flush_order_mutex_key;
 mysql_pfs_key_t	recalc_pool_mutex_key;
 mysql_pfs_key_t	purge_sys_pq_mutex_key;

storage/innobase/include/univ.i

 /*****************************************************************************
 
 Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2013, 2021, MariaDB Corporation.
+Copyright (c) 2013, 2022, MariaDB Corporation.
 Copyright (c) 2008, Google Inc.
 
 Portions of this file contain modifications contributed and copyrighted by
@@ -548,7 +548,6 @@ extern mysql_pfs_key_t ibuf_bitmap_mutex_key;
 extern mysql_pfs_key_t ibuf_mutex_key;
 extern mysql_pfs_key_t ibuf_pessimistic_insert_mutex_key;
 extern mysql_pfs_key_t log_sys_mutex_key;
-extern mysql_pfs_key_t log_cmdq_mutex_key;
 extern mysql_pfs_key_t log_flush_order_mutex_key;
 extern mysql_pfs_key_t recalc_pool_mutex_key;
 extern mysql_pfs_key_t purge_sys_pq_mutex_key;