Fix description of Prefs:Display OverviewFontSize option

Author: delphidabbler

Docs/Design/FileFormats/config.html

@@ -917,7 +917,7 @@ <h4>
     <code class="key">OverviewFontSize</code> (Integer)
   </dt>
   <dd>
-    Size of font to be used in overview pane tree view. If missing or empty the default value is <code class="value">9</code>.
+    Size of font to be used in overview pane tree view. If missing or empty the default value is the default font size of the operationg system.
   </dd>
   <dt>
     <code class="key">DetailFontSize</code> (Integer)