doc: add link to `net.Server` in tls.md

PR-URL: https://github.com/nodejs/node/pull/10109
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

doc/api/tls.md

@@ -365,7 +365,7 @@ port value of zero will assign a random port.
 This function is asynchronous. The last parameter `callback` will be called
 when the server has been bound.
 
-See `net.Server` for more information.
+See [`net.Server`][] for more information.
 
 ### server.maxConnections
 <!-- YAML