server: self context extent broken

[phymbert]

Passkey feature has been failing since a week:

https://github.com/ggerganov/llama.cpp/actions/workflows/server.yml?query=event%3Aschedule

[phymbert]

Closing as of new models support now long context and self context extent support has been removed in the server:

• server : remove self-extend features #9860