bigquery: samples are missing from docs

Internal Report:

```
python is now missing from the Sample Browser page I always use for snippet data queries: https://docs.cloud.google.com/bigquery/docs/samples/bigquery-query

It looks like the previous googleapis/python-bigquery repo was deprecated but the bigquery_query region tag wasn't moved to https://github.com/googleapis/google-cloud-python/tree/main/packages/google-cloud-bigquery
```

We should look into this, and make sure the samples made it over in the migration

(We had a similar issue with bigtable samples)