Add a modified version of the auto MPG dataset

Before, we were loading it directly from the UCI dataset repository. However, this cause connection issues and build fails. The dataset is now added directly with its respective license.

Further, removed the output of the causal discovery example notebook to ensure that it gets compiled while building.

Signed-off-by: Patrick Bloebaum <bloebp@amazon.com>

docs/source/example_notebooks/LICENSE

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+The auto MPG dataset is a modified version from: https://archive.ics.uci.edu/dataset/9/auto+mpg
+
+Reference:
+    Quinlan,R.. (1993). Auto MPG. UCI Machine Learning Repository. https://doi.org/10.24432/C5859H.
+
+Modifications done:
+- Dropped rows with nans
+- Dropped columns 'model year', 'origin' and 'car name'
+
+This dataset is licensed under a Creative Commons Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/legalcode) (CC BY 4.0) license.
+
+This allows for the sharing and adaptation of the datasets for any purpose, provided that the appropriate credit is given.