Remove trac-wiki link

sf.net pulled the plug of hosted apps including trac-wiki.  The link
to the wiki has not worked for some time now.  We submit issue to
sf.net to migrate the wiki content to current sf.net standard wiki.
When the migration is done, we'll add the link to it in the doc.

README.rst

@@ -24,9 +24,7 @@ The project page is located at http://aria2.sourceforge.net/.
 See `aria2 Online Manual
 <http://aria2.sourceforge.net/manual/en/html/>`_ (`Russian translation
 <http://aria2.sourceforge.net/manual/ru/html/>`_, `Portuguese
-translation <http://aria2.sourceforge.net/manual/pt/html/>`_) and `the
-usage examples
-<http://sourceforge.net/apps/trac/aria2/wiki/UsageExample>`_ to learn
+translation <http://aria2.sourceforge.net/manual/pt/html/>`_) to learn
 how to use aria2.
 
 Features
@@ -520,7 +518,6 @@ References
 
 * `aria2 Online Manual <http://aria2.sourceforge.net/manual/en/html/>`_
 * http://aria2.sourceforge.net/
-* http://sourceforge.net/apps/trac/aria2/wiki
 * https://github.com/tatsuhiro-t/aria2
 * `RFC 959 FILE TRANSFER PROTOCOL (FTP) <http://tools.ietf.org/html/rfc959>`_
 * `RFC 1738 Uniform Resource Locators (URL) <http://tools.ietf.org/html/rfc1738>`_

doc/manual-src/en/aria2c.rst

@@ -4072,8 +4072,6 @@ SEE ALSO
 --------
 Project Web Site: http://aria2.sourceforge.net/
 
-aria2 Wiki: http://sourceforge.net/apps/trac/aria2/wiki
-
 Metalink Homepage: http://www.metalinker.org/
 
 The Metalink Download Description Format: :rfc:`5854`