False positive in unused_closure_parameter when using backticks

[sberrevoets]

New Issue Checklist

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

Describe the bug

SwiftLint reports a false positive for unused_closure_parameter when the parameter in question is wrapped in backticks. #2006 is a similar issue (and potentially a manifestation of the same bug) but was closed.

Complete output when running SwiftLint, including the stack trace and command used

$ swiftlint lint --path Sample.swift --no-cache --enable-all-rules
Linting Swift files at paths Sample.swift
Linting 'Sample.swift' (1/1)
/Users/scott/Developer/Sample.swift:4:31: warning: Unused Closure Parameter Violation: Unused parameter "class" in a closure should be replaced with _. (unused_closure_parameter)
Done linting! Found 1 violation, 0 serious in 1 file.

Environment

• SwiftLint version (run swiftlint version to be sure)? 0.43.1
• Installation method used (Homebrew, CocoaPods, building from source, etc)? Homebrew
• Paste your configuration file: none
• Are you using nested configurations? No
• Which Xcode version are you using (check xcodebuild -version)? Xcode 12.4 12D4e
• Do you have a sample that shows the issue?

Sample.swift

internal struct Sample {
    internal func test() -> [String] {
        let classes: [String] = ["a", "b", "c"]
        return array.filter { `class` in `class`.hasPrefix("a") }
    }
}

[lhunath]

maybe we could add the bug label?

[jpsim]

Fix: #3916