doc: add unreachable code on events example

PR-URL: https://github.com/nodejs/node/pull/32364
Reviewed-By: Anna Henningsen <anna@addaleax.net>

doc/api/events.md

@@ -912,6 +912,7 @@ const { on, EventEmitter } = require('events');
     // if concurrent execution is required.
     console.log(event); // prints ['bar'] [42]
   }
+  // Unreachable here
 })();
 ```