Remove ref from combined documentation - it's now part of core.

doc/src/boost.xml

@@ -561,8 +561,6 @@
      </libraryinfo>
    </library>
 
-   <xi:include href="../../libs/bind/doc/ref.xml"/>
-
    <library name="Regex" dirname="regex" html-only="1"
             url="../../libs/regex/index.html">
      <libraryinfo>