FIX exercise placeholder comments

Author: clijo

code-exercises/01 - JAX AI Stack.ipynb

@@ -109,8 +109,8 @@
     "# print(f\"Original id(a): {original_a_id}\")\n",
     "\n",
     "# TODO: Perform an operation that reassigns 'a', e.g., a = a + 1\n",
-    "# a_new_ref = None # Placeholder\n",
-    "# new_a_id = id(a_new_ref)\n",
+    "# a = None # Placeholder\n",
+    "# new_a_id = id(a)\n",
     "# print(f\"New id(a) after 'a = a + 1': {new_a_id}\")\n",
     "\n",
     "# TODO: Check if original_a_id is different from new_a_id\n",