Remove individual URL overrides for LLM service (#30290)

This PR removes the individual URL overrides for the LLM service.

We initially had `ZED_PREDICT_EDITS_URL` to allow for directing traffic
to the LLM Worker back when there was still the split of the
Collab-based LLM Service and the Cloudflare-based LLM Worker.

But now that all of the LLM functionality has been moved into the
Worker, we can just direct all traffic there.

Release Notes:

- N/A

crates/web_search_providers/src/cloud.rs

@@ -77,13 +77,9 @@ async fn perform_web_search(
 
     let token = llm_api_token.acquire(&client).await?;
 
-    let request_builder = http_client::Request::builder().method(Method::POST);
-    let request_builder = if let Ok(web_search_url) = std::env::var("ZED_WEB_SEARCH_URL") {
-        request_builder.uri(web_search_url)
-    } else {
-        request_builder.uri(http_client.build_zed_llm_url("/web_search", &[])?.as_ref())
-    };
-    let request = request_builder
+    let request = http_client::Request::builder()
+        .method(Method::POST)
+        .uri(http_client.build_zed_llm_url("/web_search", &[])?.as_ref())
         .header("Content-Type", "application/json")
         .header("Authorization", format!("Bearer {token}"))
         .header(CLIENT_SUPPORTS_EXA_WEB_SEARCH_PROVIDER_HEADER_NAME, "true")