Remove unused documentation file

doc/src/sgml/contacts.sgml

-<!-- doc/src/sgml/contacts.sgml -->
-
-<appendix label="B" id="contacts">
-<title>Contacts</title>
-
-<!--
-<para>
-Support for <productname>PostgreSQL</productname> comes primarily from
-this printed documentation, the web-based mailing list archives,
-and the mailing lists themselves.
-</para>
-
-<sect1 id="mailing-list">
-<title>Mailing Lists</title>
-
-<para>
-Refer to the introduction in this manual or to the
-<productname>PostgreSQL</productname>
-<ulink url="https://www.postgresql.org">web page</ulink>
-for subscription information to the no-cost mailing lists.
-</para>
-
-<sect1 id="people">
-<title>People</title>
--->
-</appendix>

doc/src/sgml/filelist.sgml

@@ -156,7 +156,6 @@
 <!ENTITY xml2            SYSTEM "xml2.sgml">
 
 <!-- appendixes -->
-<!ENTITY contacts   SYSTEM "contacts.sgml">
 <!ENTITY datetime   SYSTEM "datetime.sgml">
 <!ENTITY docguide   SYSTEM "docguide.sgml">
 <!ENTITY errcodes   SYSTEM "errcodes.sgml">