samples: add samples for object retention

[ddelgrosso1]

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Fixes #2408 🦕

[snippet-bot[bot]]

Here is the summary of changes.

You are about to add 2 region tags.

- [samples/createBucketWithObjectRetention.js:23](https://github.com/ddelgrosso1/nodejs-storage/blob/52c7f398e4dce52947e354654b15ba442f606a56/samples/createBucketWithObjectRetention.js#L23), tag `storage_create_bucket_with_object_retention` - [samples/setObjectRetentionPolicy.js:27](https://github.com/ddelgrosso1/nodejs-storage/blob/52c7f398e4dce52947e354654b15ba442f606a56/samples/setObjectRetentionPolicy.js#L27), tag `storage_set_object_retention_policy`

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[generated-files-bot[bot]]

Warning: This pull request is touching the following templated files:

• README.md - README.md is managed by synthtool. However, a partials file can be used to update the README, e.g.: https://github.com/googleapis/nodejs-storage/blob/main/.readme-partials.yaml
• samples/README.md - samples/README.md is managed by synthtool. However, a partials file can be used to update the README, e.g.: https://github.com/googleapis/nodejs-storage/blob/main/.readme-partials.yaml