doc: correct broken link in net.markdown

Fixes broken link to Readable Stream documentation.

Fixes: https://github.com/joyent/node/issues/8464
PR-URL: https://github.com/joyent/node/pull/8756
Reviewed-by: Chris Dickinson <christopher.s.dickinson@gmail.com>

doc/api/net.markdown

@@ -608,6 +608,6 @@ Returns true if input is a version 6 IP address, otherwise returns false.
 [EventEmitter]: events.html#events_class_events_eventemitter
 ['listening']: #net_event_listening
 [server.getConnections()]: #net_server_getconnections_callback
-[Readable Stream]: stream.html#stream_readable_stream
+[Readable Stream]: stream.html#stream_class_stream_readable
 [stream.setEncoding()]: stream.html#stream_stream_setencoding_encoding
 [dns.lookup()]: dns.html#dns_dns_lookup_domain_family_callback