refactor,chore(egen) : refactored code according to template guidelines

[Jayakrishna2801]

This PR includes the following updates to the get_started_with_bqml_training.ipynb notebook:
1.Replace REGION with LOCATION.
2.Removes IS_TESTING condition.
3.Adds colab enterprise logo with link.
4.Makes Heading changes according to template guidelines.
5.Fix unnecessary "``" code highlight usage.
6.Adds Colab authentication and kernal restart steps.
7.removed unnecessary code

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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.
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• 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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[kittyabs]

Numerous required edits

[katiemn]

/gcbrun