Route all LLM traffic through cloud.zed.dev (#34404)

This PR makes it so all LLM traffic is routed through `cloud.zed.dev`.

We're already routing `llm.zed.dev` to `cloud.zed.dev` on the server,
but we want to standardize on `cloud.zed.dev` moving forward.

Release Notes:

- N/A

Cargo.lock

@@ -9036,7 +9036,6 @@ dependencies = [
  "credentials_provider",
  "deepseek",
  "editor",
- "feature_flags",
  "fs",
  "futures 0.3.31",
  "google_ai",
@@ -18390,7 +18389,6 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "client",
- "feature_flags",
  "futures 0.3.31",
  "gpui",
  "http_client",