doc: unify layout with Google client libraries

[tswast]

Towards #367

[snippet-bot]

Here is the summary of changes.

You are about to add 8 region tags.

• docs/intro.rst:33, tag bigquery_pandas_gbq_read_gbq_simple
• docs/intro.rst:63, tag bigquery_pandas_gbq_to_gbq_simple
• docs/reading.rst:12, tag bigquery_pandas_gbq_read_gbq_simple
• docs/reading.rst:43, tag bigquery_pandas_gbq_read_gbq_legacy
• docs/writing.rst:12, tag bigquery_pandas_gbq_to_gbq_simple
• samples/snippets/read_gbq_legacy.py:13, tag bigquery_pandas_gbq_read_gbq_legacy
• samples/snippets/read_gbq_simple.py:11, tag bigquery_pandas_gbq_read_gbq_simple
• samples/snippets/to_gbq_simple.py:11, tag bigquery_pandas_gbq_to_gbq_simple

You are about to delete 8 region tags.

• docs/source/intro.rst:33, tag bigquery_pandas_gbq_read_gbq_simple
• docs/source/intro.rst:63, tag bigquery_pandas_gbq_to_gbq_simple
• docs/source/reading.rst:12, tag bigquery_pandas_gbq_read_gbq_simple
• docs/source/reading.rst:43, tag bigquery_pandas_gbq_read_gbq_legacy
• docs/source/writing.rst:12, tag bigquery_pandas_gbq_to_gbq_simple
• samples/read_gbq_legacy.py:13, tag bigquery_pandas_gbq_read_gbq_legacy
• samples/read_gbq_simple.py:11, tag bigquery_pandas_gbq_read_gbq_simple
• samples/to_gbq_simple.py:11, tag bigquery_pandas_gbq_to_gbq_simple

---

This comment is generated by snippet-bot.
If you find problems with this result, please file an issue at:
https://github.com/googleapis/repo-automation-bots/issues.
To update this comment, add snippet-bot:force-run label or use the checkbox below:

• Refresh this comment