docs: show common job properties in get_job and cancel_job samples

[tswast]

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Towards internal issue 199162556 🦕

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/snippets/manage_job_cancel.py:15, tag bigquery_cancel_job
• samples/snippets/manage_job_get.py:15, tag bigquery_get_job

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