fix(engines): Revert engine back to 16

[benmvp]

octokit#430 upgraded the Node version to 18, but as a fix (instead of a breaking change). So it breaks consumers of the library (such as semantic-release) that are still on Node 16.

Resolves octokit#431

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Behavior

Before the change?

• Able to install a package using @ocktokit/plugin-retry with Node 16.

After the change?

• Unable to install a package using @ocktokit/plugin-retry with Node 16 because it requires Node 18.

Other information

n/a

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Additional info

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Added the appropriate label for the given change

Does this introduce a breaking change?

It doesn't. The previous PR did

Please see our docs on breaking changes to help!

• Yes (Please add the Type: Breaking change label)
• No

If Yes, what's the impact:

• N/A

Pull request type

Please add the corresponding label for change this PR introduces:

• Bugfix: Type: Bug
• Feature/model/API additions: Type: Feature
• Updates to docs or samples: Type: Documentation
• Dependencies/code cleanup: Type: Maintenance

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