collab: Remove code for embeddings (#29310)

This PR removes the embeddings-related code from collab and the
protocol, as we weren't using it anywhere.

Release Notes:

- N/A

crates/semantic_index/src/embedding.rs

@@ -1,9 +1,7 @@
-mod cloud;
 mod lmstudio;
 mod ollama;
 mod open_ai;
 
-pub use cloud::*;
 pub use lmstudio::*;
 pub use ollama::*;
 pub use open_ai::*;