updated dag viz for contribs

[zilto]

I recreated the DAG viz for the contribs. Sometimes it involved rerunning notebooks cells or changing the orientation of the DAG for better readability.

Also:

• Removed duplicated cell and unused import from XGBoost + Optuna contrib
• Replaced the deprecated PyPDF2 by pypdf for text summarization contrib

[sweep-ai]

Apply Sweep Rules to your PR?

• Apply: All new business logic should have corresponding unit tests.
• Apply: Refactor large functions to be more modular.
• Apply: Add docstrings to all functions and file headers.