BigQuery: refactor bigquery_query_params_* code samples to pass query_parameters to QueryJobConfig constructor

[tswast]

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.

google-cloud-python/bigquery/docs/snippets.py

Lines 1868 to 1873 in 518931b

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

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.

[emar-kar]

Since I’m already working with the snippets refactoring #9495, I assume this should be assigned to me as well.