assistant2: Remove "Tools" switch (#26485)

This PR removes the "Tools" switch from Assistant 2, as we can manage
tools from the tool selector now.

Release Notes:

- N/A

crates/assistant2/src/thread.rs

@@ -342,12 +342,10 @@ impl Thread {
         &mut self,
         model: Arc<dyn LanguageModel>,
         request_kind: RequestKind,
-        use_tools: bool,
         cx: &mut Context<Self>,
     ) {
         let mut request = self.to_completion_request(request_kind, cx);
-
-        if use_tools {
+        request.tools = {
             let mut tools = Vec::new();
 
             if self.tools.is_scripting_tool_enabled() {
@@ -366,8 +364,8 @@ impl Thread {
                 }
             }));
 
-            request.tools = tools;
-        }
+            tools
+        };
 
         self.stream_completion(request, model, cx);
     }
@@ -753,7 +751,7 @@ impl Thread {
             Vec::new(),
             cx,
         );
-        self.send_to_model(model, RequestKind::Chat, true, cx);
+        self.send_to_model(model, RequestKind::Chat, cx);
     }
 
     /// Cancels the last pending completion, if there are any pending.