fix(environments): swallow 404 not found errors

[acouvreur]

When an environment no longer exist, the deletion call should not throw back an error.

The resource is in the desired state, gone.

Resolves #3131

Before the change?

• Environments deleted externally would make the deletion fail

After the change?

• Environments deleted externally will be deleted from the state

Pull request checklist

• Schema migrations have been created if needed (example)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[github-actions]

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[stevehipwell]

LGTM