Remove unneeded anonymous lifetimes from gpui::Context (#27686)

This PR removes a number of unneeded anonymous lifetimes from usages of
`gpui::Context`.

Release Notes:

- N/A

crates/assistant2/src/active_thread.rs

@@ -530,7 +530,7 @@ impl ActiveThread {
         caption: impl Into<SharedString>,
         icon: IconName,
         window: &mut Window,
-        cx: &mut Context<'_, ActiveThread>,
+        cx: &mut Context<ActiveThread>,
     ) {
         if window.is_window_active()
             || !self.notifications.is_empty()
@@ -1791,7 +1791,7 @@ impl ActiveThread {
             })
     }
 
-    fn dismiss_notifications(&mut self, cx: &mut Context<'_, ActiveThread>) {
+    fn dismiss_notifications(&mut self, cx: &mut Context<ActiveThread>) {
         for window in self.notifications.drain(..) {
             window
                 .update(cx, |_, window, _| {

crates/assistant2/src/thread.rs

@@ -1242,7 +1242,7 @@ impl Thread {
         input: serde_json::Value,
         messages: &[LanguageModelRequestMessage],
         tool: Arc<dyn Tool>,
-        cx: &mut Context<'_, Thread>,
+        cx: &mut Context<Thread>,
     ) {
         let task = self.spawn_tool_use(tool_use_id.clone(), messages, input, tool, cx);
         self.tool_use