Fix code block syntax

Author: GaneshChandrasekaran-zz

components/lock.rst

@@ -519,7 +519,7 @@ can be two running containers in parallel.
 ZookeeperStore
 ~~~~~~~~~~
 
-The way ZookeeperStore works is by maintaining locks in ephemeral nodes within `PHP_LOCK_NODE` on the server. That means that by using
+The way ZookeeperStore works is by maintaining locks in ephemeral nodes within ``PHP_LOCK_NODE`` on the server. That means that by using
 the :ref:`ZookeeperStore <lock-store-zookeeper>` the locks will be automatically released at the end of the session
 in case the client cannot unlock for any reason.