gh-135329: Use longer timeout in pyrepl test_repl_eio() (#139503)

Replace hardcoded 5 seconds with support.SHORT_TIMEOUT.

Fix the following error on slow CI such as GitHub Action UBSan:

test test_pyrepl failed -- Traceback (most recent call last):
  File "Lib/test/test_pyrepl/test_unix_console.py", line 362, in test_repl_eio
    _, err = proc.communicate(timeout=5)  # sleep for pty to settle
             ~~~~~~~~~~~~~~~~^^^^^^^^^^^
  File "Lib/subprocess.py", line 1219, in communicate
    stdout, stderr = self._communicate(input, endtime, timeout)
                     ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "Lib/subprocess.py", line 2126, in _communicate
    self._check_timeout(endtime, orig_timeout, stdout, stderr)
    ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "Lib/subprocess.py", line 1266, in _check_timeout
    raise TimeoutExpired(
    ...<2 lines>...
            stderr=b''.join(stderr_seq) if stderr_seq else None)
subprocess.TimeoutExpired: Command '[...]' timed out after 5 seconds