documentation update: include bigquery_dataset resource in examples

[Bjorn248]

This is intended to show how the dataset_id attribute should be used to reference an existing bigquery dataset. This also mirrors the format of the bigquery_dataset_access documentation. This is intended to avoid confusion. I recently ran into this issue myself, where I only viewed the bigquery_dataset_iam docs and not the bigquery_dataset_access docs, and I used the id attribute instead of the dataset_id attribute, which caused me some trouble haha.

[github-actions]

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