GEOS-6668: Fix WMS 1.1.1 CITE failure.

This modifies the DTD to match the new CITE requirements (per CITE-866).

An alternative implementation would be to get the http://schemas.opengis.net/wms/1.1.1/capabilities_1_1_1.dtd
version and copy that in, instead of modifying the existing file. Slightly different implementation, same effect.