Add Faraday DEFAULT_EXCEPTIONS for when retry middleware is available

[DougEdey]

Resolves #1188

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Behavior

Before the change?

• Octokit would not retry on timeouts

After the change?

• Octokit does retry on timeouts

Other information

• It's pretty straightforward, I can see the original issue marks this as a breaking change.

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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?

Please see our docs on breaking changes to help!

• Yes (Please add the Type: Breaking change label)
• No (I don't think so)

If Yes, what's the impact:

• This could be a breaking change since Octokit will now retry on errors it didn't before, but Faraday retry middleware #1021 wasn't marked as a breaking change,

Pull request type

I want to mark this as a bug, but I can understand if it's a feature!

[DougEdey]

cc @tjoyal

[nickfloyd]

Hey @DougEdey thank you for this change! ❤️