remove extra quote from disabled-command message (#3035)

there was an extra ' floating around for some reason.

codex-rs/tui/src/chatwidget.rs

@@ -766,7 +766,7 @@ impl ChatWidget {
     fn dispatch_command(&mut self, cmd: SlashCommand) {
         if !cmd.available_during_task() && self.bottom_pane.is_task_running() {
             let message = format!(
-                "'/'{}' is disabled while a task is in progress.",
+                "'/{}' is disabled while a task is in progress.",
                 cmd.command()
             );
             self.add_to_history(history_cell::new_error_event(message));