`TestPyReplAutoindent.test_auto_indent_default()` misses `self.assertEqual()`

# Bug report

### Bug description:

The [test_auto_indent_default()](https://github.com/python/cpython/blob/main/Lib/test/test_pyrepl/test_pyrepl.py#L441-L453) forgets to run the `input_code`.

### CPython versions tested on:

3.14, 3.15

### Operating systems tested on:

Linux


### Linked PRs
* gh-133640
* gh-133646
* gh-133647