Update lxml to 6.0.3

[pyup-bot]

This PR updates lxml from 6.0.2 to 6.0.3.

Changelog

6.0.3

==================

Bugs fixed
----------

* Several out of memory error cases now raise ``MemoryError`` that were not handled before.

* Slicing with large step values (outside of ``+/- sys.maxsize``) could trigger undefined C behaviour.

* LP2125399: Some failing tests were fixed or disabled in PyPy.

* LP2138421: Memory leak in error cases when setting the ``public_id`` or ``system_url`` of a document.

* Memory leak in case of a memory allocation failure when copying document subtrees.

* When mapping an XPath result to Python failed, the result memory could leak.

* When preparing an XSLT transform failed, the XSLT parameter memory could leak.

Other changes
-------------

* Built using Cython 3.2.4.

* Binary wheels use zlib 1.3.2.

Links

• PyPI: https://pypi.org/project/lxml
• Changelog: https://data.safetycli.com/changelogs/lxml/
• Homepage: https://lxml.de/

[pyup-bot]

Closing this in favor of #2896