Is your feature request related to a problem? Please describe.

The code samples for using query parameters are a bit hard to follow because they create several temporary variables.

The code samples are still in snippets.py. Ideally these samples would be moved to the samples/ directory.

The code samples supply a location argument for queries, even though this can now be autodetected for queries in all regions.

Describe the solution you'd like
A clear and concise description of what you want to happen.

• Move any bigquery_query_params_... samples to the samples/ directory.
• Remove the location argument from the query() method in the moved code samples
• Use the query_parameters argument in the constructor to QueryJobConfig (added in BigQuery: Add properties to job config constructors #6397).

job_config = bigquery.QueryJobConfig(
    query_parameters=[
        bigquery.ScalarQueryParameter("corpus", "STRING", "romeoandjuliet"),
        bigquery.ScalarQueryParameter("min_word_count", "INT64", 250),
    ],
)

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

N/A

Additional context
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Reported by customer in internal issue 143862711.