fix up URLs in cave_data files for ${subarea} -> '1623'

noinfo/cave_data/1623-196.html

@@ -32,8 +32,8 @@
 <depth></depth>
 <extent></extent>
 <survex_file>caves/196/196.svx</survex_file>
-<description_file>smkridge/196.htm</description_file>
-<url>smkridge/196.htm</url>
+<description_file>1623/196.htm</description_file>
+<url>1623/196.htm</url>
 </cave>
 </body>
 </html>