chore, fix(egen): follows new template, markdown updates and fixes

[krishr2d2]

This PR includes the following updates to the `challenger_vs_blessed_deployment_method.ipynb` notebook:

• Change REGION to LOCATION
• Remove IS_TESTING condition at cleaning step
• Adds IS_COLAB in the service account setup
• Removes USER in the installation
• Moves the deletion of local files to the cleaning up section
• Add Colab Enterprise link and other updates from new template.
• Reorganizes the heading styles to match the steps.
• Removes unnecessary code highlights
• Removes future tense
• Contracts words like "do not" --> "don't"
• Update K80 GPU with T4 GPU

REQUIRED: Fill out the below checklists or remove if irrelevant

1. If you are opening a PR for Official Notebooks under the notebooks/official folder, follow this mandatory checklist:

• Use the notebook template as a starting point.
• Follow the style and grammar rules outlined in the above notebook template.
• Verify the notebook runs successfully in Colab since the automated tests cannot guarantee this even when it passes.
• Passes all the required automated checks. You can locally test for formatting and linting with these instructions.
• You have consulted with a tech writer to see if tech writer review is necessary. If so, the notebook has been reviewed by a tech writer, and they have approved it.
• This notebook has been added to the CODEOWNERS file under the Official Notebooks section, pointing to the author or the author's team.
• The Jupyter notebook cleans up any artifacts it has created (datasets, ML models, endpoints, etc) so as not to eat up unnecessary resources.

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[gericdong]

/gcbrun

[kittyabs]

numerous edits

[katiemn]

/gcbrun