Add plots.font to properties file documentation

RE #28597

docs/source/concepts/PropertiesFile.rst

@@ -262,6 +262,8 @@ Plotting Settings
 +---------------------------------+------------------------------------------------------------------+---------------------+
 |``plots.ShowMinorGridlines``     |Whether to show minor gridlines on plots                          | ``On``, ``Off``     |
 +---------------------------------+------------------------------------------------------------------+---------------------+
+|``plots.font``                   |The default font for labels and titles on plots.                  |``Helvetica``        |
++---------------------------------+------------------------------------------------------------------+---------------------+
 |``plots.xAxesScale``             |The default x scale on 1d plots                                   |``Linear``, ``Log``  |
 +---------------------------------+------------------------------------------------------------------+---------------------+
 |``plots.yAxesScale``             |The default y scale on 1d plots                                   |``Linear``, ``Log``  |