feat: Add metadata SDK sample for delete method.

[SinaChavoshi]

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Fixes #<issue_number_goes_here> 🦕

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• samples/model-builder/experiment_tracking/delete_artifact_sample.py:18, tag aiplatform_sdk_delete_artifact_sample
• samples/model-builder/experiment_tracking/delete_context_sample.py:18, tag aiplatform_sdk_delete_context_sample
• samples/model-builder/experiment_tracking/delete_execution_sample.py:18, tag aiplatform_sdk_delete_execution_sample

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