Bump lxml to v6.0.3

[mxamin]

No description provided.

[Copilot]

Pull request overview

This PR updates the pinned lxml dependency version used by the project’s pip requirements files, including the documentation build requirements.

Changes:

• Bump lxml from 6.0.2 to 6.0.3 in the main requirements.txt.
• Bump lxml from 6.0.2 to 6.0.3 in doc/source/requirements.txt (Read the Docs install requirements).

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
requirements.txt	Updates the pinned lxml version used by -r requirements.txt consumers (e.g., tests/dev installs).
doc/source/requirements.txt	Keeps docs build dependencies aligned by pinning lxml to the same updated version.

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