Updated 12 example notebooks to run on Colab. Fixes #385

[codell2]

This PR addresses issue #385 by updating 12 example Jupyter notebooks in the examples directory to work out of the box on Google Colab.

Changes Made:

• Added "Open in Colab" buttons to the top of each notebook.
• Adjusted file paths and dependencies to ensure compatibility with the Colab environment.

List of Updated Files:

• examples/demo_FACTS.ipynb
• examples/demo_gerryfair.ipynb
• examples/demo_json_explainers.ipynb
• examples/demo_lfr.ipynb
• examples/demo_mdss_classifier.ipynb
• examples/demo_mdss_detector.ipynb
• examples/demo_meta_classifier.ipynb
• examples/demo_ot_metric.ipynb
• examples/demo_reject_option_classification.ipynb
• examples/demo_reweighing_preproc.ipynb
• examples/demo_short_gerryfair_test.ipynb
• examples/tutorial_medical_expenditure.ipynb