docs: add ml tutorial for Evaluate the model

[rey-esp]

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Fixes # 🦕

[conventional-commit-lint-gcf[bot]]

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[snippet-bot[bot]]

Here is the summary of changes.

You are about to add 1 region tag.

• samples/snippets/linear_regression_tutorial_test.py:40, tag bigquery_dataframes_bqml_linear_evaluate

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