Fix #1901: Install system dependencies for lxml in workflow and Docker

[7uyash]

This PR fixes issue #1990

I found that publishing-check.yml and the Dockerfile were missing the system libraries required to compile lxml on Ubuntu 24.04.
Changes:

• Added libxml2-dev and libxslt1-dev to .github/workflows/publishing-check.yml.
• Added the same dependencies to the Dockerfile.

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