false positives on redundant_objc_attribute

[weakfl]

New Issue Checklist

• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

Describe the bug

The redundant_objc_attribute rule yields false positives if a private function needs to be marked @objc in order to be used with a selector.

According to the documentation this should be not triggering, but it is.

Environment

• SwiftLint 0.29.1
• Homebrew

Example

bar.addTarget(self, action: #selector(foo), for: .touchUpInside)
// This triggers a violation:
@objc private func foo() {
}

[marcelofabri]

Closed in #2501