Add acic 2016

[vortex-wq]

Checklist

• Added the ACIC 2016 dataset under simulated/acic-2016/
• Included the preprocessed dataset file (acic.2016.sim.1.mixed.txt)
• Added a dataset README with source and column descriptions
• Preserved the original dataset format and metadata where applicable
• Verified the dataset structure locally
• Waiting for maintainer review

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  Yes

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Issue number(s) that this pull request fixes

Partly fixes: pgmpy/pgmpy#2937

Related issue(s): pgmpy/pgmpy#2419

Companion PR (if applicable): pgmpy/pgmpy#3523

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List of changes to the codebase in this pull request

• Added the ACIC 2016 dataset under simulated/acic-2016/, the preprocessed dataset file acic.2016.sim.1.mixed.txt, a readme.txt describing the dataset, its source, and the included variables.