Remove duplicate message bubble icon (#27699)

Release Notes:

- N/A

crates/assistant2/src/context.rs

@@ -50,7 +50,7 @@ impl ContextKind {
             ContextKind::Directory => IconName::Folder,
             ContextKind::Symbol => IconName::Code,
             ContextKind::FetchedUrl => IconName::Globe,
-            ContextKind::Thread => IconName::MessageCircle,
+            ContextKind::Thread => IconName::MessageBubbles,
         }
     }
 }

crates/assistant2/src/context_picker.rs

@@ -84,7 +84,7 @@ impl ContextPickerMode {
             Self::File => IconName::File,
             Self::Symbol => IconName::Code,
             Self::Fetch => IconName::Globe,
-            Self::Thread => IconName::MessageCircle,
+            Self::Thread => IconName::MessageBubbles,
         }
     }
 }

crates/assistant2/src/context_picker/completion_provider.rs

@@ -152,7 +152,7 @@ impl ContextPickerCompletionProvider {
         let icon_for_completion = if recent {
             IconName::HistoryRerun
         } else {
-            IconName::MessageCircle
+            IconName::MessageBubbles
         };
         let new_text = format!("@thread {}", thread_entry.summary);
         let new_text_len = new_text.len();
@@ -164,7 +164,7 @@ impl ContextPickerCompletionProvider {
             source: project::CompletionSource::Custom,
             icon_path: Some(icon_for_completion.path().into()),
             confirm: Some(confirm_completion_callback(
-                IconName::MessageCircle.path().into(),
+                IconName::MessageBubbles.path().into(),
                 thread_entry.summary.clone(),
                 excerpt_id,
                 source_range.start,

crates/assistant2/src/context_picker/thread_context_picker.rs

@@ -197,7 +197,7 @@ pub fn render_thread_context_entry(
                 .gap_1p5()
                 .max_w_72()
                 .child(
-                    Icon::new(IconName::MessageCircle)
+                    Icon::new(IconName::MessageBubbles)
                         .size(IconSize::XSmall)
                         .color(Color::Muted),
                 )