CDRIVER-3588 update comment

Author: kevinAlbs

src/libmongoc/tests/test-mongoc-sample-commands.c

@@ -3472,8 +3472,7 @@ with_transaction_example (bson_error_t *error)
 
    client = get_client ();
 
-   /* Prereq: Create collections. CRUD operations in transactions must be on
-    * existing collections. */
+   /* Prereq: Create collections. */
    wc = mongoc_write_concern_new ();
    mongoc_write_concern_set_wmajority (wc, 1000);
    insert_opts = bson_new ();