feat(genai/tuning): Add sample for canceling tuning jobs

[Kef131]

Description

Fixes b/542305811

Changes:

• Created genai/tuning/tuning_job_cancel.py using client.tunings.cancel() with region tag googlegenaisdk_tuning_job_cancel.
• Added unit test test_tuning_job_cancel in genai/tuning/test_tuning_examples.py.
• Safeguarded the output_gcs_uri test fixture teardown against permission errors during local test runs.

Passed tests

Checklist

Testing

• I have tested this change on a live environment and verified it works as intended.

Compliance & Style

• I have followed the Sample Guidelines.
• The README is updated with all relevant information (if applicable).
• If this PR adds a new sample directory: I updated the CODEOWNERS file.

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Post-Approval Actions

• Please merge this PR for me once it is approved

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• genai/tuning/tuning_job_cancel.py:17, tag googlegenaisdk_tuning_job_cancel

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[gemini-code-assist]

Code Review

This pull request introduces a new script tuning_job_cancel.py to cancel GenAI tuning jobs, along with corresponding unit tests in test_tuning_examples.py. Feedback on the changes suggests avoiding catching a broad Exception during GCS cleanup in the test setup, recommending catching google.api_core.exceptions.GoogleAPIError instead to prevent masking unrelated errors.