[doc] fix documentation test failure (#36855)

add a dash.

Signed-off-by: Lonnie Liu <lonnie@anyscale.com>

doc/source/cluster/running-applications/job-submission/ray-client.rst

@@ -287,7 +287,7 @@ If a ``working_dir`` is specified in the runtime env, when running ``ray.init()`
 Ray workers are started in the ``/tmp/ray/session_latest/runtime_resources/_ray_pkg_<hash of directory contents>`` directory on the cluster. This means that relative paths in the remote tasks and actors in the code will work on the laptop and on the cluster without any code changes. For example, if the ``working_dir`` on the laptop contains ``data.txt`` and ``run.py``, inside the remote task definitions in ``run.py`` one can just use the relative path ``"data.txt"``. Then ``python run.py`` will work on my laptop, and also on the cluster. As a side note, since relative paths can be used in the code, the absolute path is only useful for debugging purposes.
 
 Troubleshooting
---------------
+---------------
 
 Error: Attempted to reconnect a session that has already been cleaned up 
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