Clarify certificate setup for self-hosted

Self-hosted instances often run behind a private CA, and the deploy guide only showed one client's certificate setup while still documenting the retired v1 Python client.

• Removed the legacy Python SDK v1 examples from the self-hosting deploy guide, leaving OpenHTF and the current Python SDK.
• Added certificate guidance for every client: the Python SDK accepts a custom certificate directly, while OpenHTF and the C++ and MATLAB SDKs use the standard OpenSSL environment variable.
• Documented that the Rust SDK cannot connect to an instance using a private certificate authority yet.