Autocorrect for implicit_return breaks when implicit returns are nested

[mildm8nnered]

New Issue Checklist

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

Describe the bug

autocorrect for implicit_return breaks when implicit returns are nested. Running --fix for implicit_return on the SwiftLint source (0.55.1 for example)

In YamlParser.swift

    static func constructExpandingEnvVars(env: [String: String]) -> (_ scalar: Node.Scalar) -> String? {
        return { (scalar: Node.Scalar) -> String? in
            return scalar.string.expandingEnvVars(env: env)
        }
    }

becomes

    static func constructExpandingEnvVars(env: [String: String]) -> (_ scalar: Node.Scalar) -> String? {
        { (scalar: Node.Scalar) -> String? in
            return string.expandingEnvVars(env: env)
        }
    }

which fails to compile with

/Users/martin.redington/Documents/Source/SwiftLint/Source/SwiftLintCore/Models/YamlParser.swift:44:20: error: cannot find 'string' in scope
            return string.expandingEnvVars(env: env)

Multiple other similar cases in the SwiftLint source.