Fix wording of confirm_deprovision docs

Change-Id: Iacd18fe6b6402f73391fa6451a40354daef125d7

doc/source/administration/overcloud.rst

@@ -183,7 +183,7 @@ Deprovisioning The Cloud
    This step will power down the overcloud hosts and delete their nodes'
    instance state from the seed's ironic service. This command will print a
    list of hosts which will be deprovisioned, you must type ``yes`` to confirm.
-   To automatically confirm, pass the variable ``-e confirm_deprovision=yes``.
+   To automatically confirm, pass the arguments ``-e confirm_deprovision=yes``.
 
 To deprovision the overcloud::