ostel fix

Ostel again points to non-existing category **sip-server** instead sip-server**s** and it is included in voice & video while it belongs to sip-servers and only the link that points to Ostel belongs to that subcategory (e.g: Get a free Sip-account for Jitsi and/or CSipSimple with The Guardian Project’s Ostel service).

www.geticeweasel.org returns 503 Service Unavailable