language_model: Remove use_any_tool method from LanguageModel (#27930)

This PR removes the `use_any_tool` method from the `LanguageModel`
trait.

It was not being used anywhere, and doesn't really fit in our new tool
use story.

Release Notes:

- N/A

crates/language_models/src/provider/copilot_chat.rs

@@ -1,4 +1,3 @@
-use std::future;
 use std::sync::Arc;
 
 use anyhow::{Result, anyhow};
@@ -293,17 +292,6 @@ impl LanguageModel for CopilotChatLanguageModel {
         }
         .boxed()
     }
-
-    fn use_any_tool(
-        &self,
-        _request: LanguageModelRequest,
-        _name: String,
-        _description: String,
-        _schema: serde_json::Value,
-        _cx: &AsyncApp,
-    ) -> BoxFuture<'static, Result<BoxStream<'static, Result<String>>>> {
-        future::ready(Err(anyhow!("not implemented"))).boxed()
-    }
 }
 
 impl CopilotChatLanguageModel {