fix: Correct logic for github_actions_organization_workflow_permissions

[stevehipwell]

Resolves #ISSUE_NUMBER

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Before the change?

• The github_actions_organization_workflow_permissions resource can't set can_approve_pull_request_reviews to false

After the change?

• The github_actions_organization_workflow_permissions resource works correctly

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]

CC @deiga this is why we can't use d.GetOk() for booleans; ok is false for zero values.