Fix accessors docs build

What happened?

• Python 3.14.7 added a docstring to typing._GenericAlias. In Python 3.14.6 they were code comments.
• This caused sphinx to parse the _GenericAlias docstring instead of the accessor and throw an error.

Fixed in PR: https://github.com/xarray-contrib/sphinx-autosummary-accessors/pull/171

Reference: https://github.com/pydata/xarray/pull/11570

What did you expect to happen?

No response

Steps to reproduce

No response

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Anything else we need to know?

No response

Environment

Start by reviewing the referenced sphinx-autosummary-accessors PR and the Python 3.14.7 change to typing._GenericAlias. Reproduce the accessors documentation build with Python 3.14.7, then verify that it completes without Sphinx parsing the _GenericAlias docstring.