Also change Expert Configuration option's description wording

.. after the changed string in Compatibility options done in commit
ae0edc47.

Change-Id: I6708ef76207a02915c6ec883cc3c7c5d0245ae40
Reviewed-on: https://gerrit.libreoffice.org/54524Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

officecfg/registry/schema/org/openoffice/Office/Compatibility.xcs

@@ -118,7 +118,7 @@
       </prop>
       <prop oor:name="SubtractFlysAnchoredAtFlys" oor:type="xs:boolean" oor:nillable="false">
         <info>
-          <desc>Use LibreOffice 4.3 anchoring paint order</desc>
+          <desc>Tolerate white lines of PDF page backgrounds for compatibility with old documents (Use LibreOffice 4.3 anchoring paint order)</desc>
         </info>
         <value>false</value>
       </prop>