docs(samples): Improving snapshot samples

[m-strzelczyk]

Improving the code snippets for disk snapshots, so they can be used on this page: Create and manage disk snapshots

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/snippets/snapshots/delete_by_filter.py:23, tag compute_snapshot_delete_by_filter
• samples/snippets/snapshots/get.py:22, tag compute_snapshot_get

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