[css2] Fixed typo "visble"

--HG--
extra : convert_revision : svn%3A73dc7c4b-06e6-40f3-b4f7-9ed1dbc14bfc/trunk%402163

Author: bert-github

css2/properties/properties.db

@@ -377,7 +377,7 @@ table-cell | table-caption | none | inherit;;
 
 /* visibility;;
   visible | hidden | collapse | inherit;;
-  visble;;
+  visible;;
   *;;
   yes;;
   N/A;;