Increasing the depth of the PDF TOC

[john-science]

What is the change? Why is it being made?

close #2414

SCR Information

Change Type: docs

One-Sentence Rationale: TBD

One-line Impact on Requirements: NA

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify any new/changed code.
• The documentation is still up-to-date in the doc folder.
• The code style follows good practices.
• The dependencies are still up-to-date in pyproject.toml.

[john-science]

No success yet.