Update monitors vars to include ones (!93)

docs/source_docs/user_guide/inputs/output/monitors.rst

@@ -141,6 +141,8 @@ The following table lists all the fluid phase variables that can be monitored:
 +--------------------------+-----------------------------------------------------------------------------------------+
 |                          | Description                                                                             |
 +==========================+=========================================================================================+
+| ones                     | values of :math:`phi` is set to 1.                                                      |
++--------------------------+-----------------------------------------------------------------------------------------+
 | ep_g                     | fluid volume fraction                                                                   |
 +--------------------------+-----------------------------------------------------------------------------------------+
 | p_g                      | fluid pressure                                                                          |