`unused_setter_value` incorrectly gets triggered for an empty setter

New Issue Checklist

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

Describe the bug

The following code gets reported as a vioation of the unused_setter_value rule, even though it was one of the examples explicitly cited as being non-offending.

override var aValue: String {
  get {
    return Persister.shared.aValue
  }
  set() { }

There might be a meta-issue here, about why the example didn't cause a test failure.

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

$ swiftlint lint

Environment

• SwiftLint version: 0.46.3

• Installation method used: Homebrew

• Which Xcode version are you using (check xcodebuild -version)? Xcode 13.2.1 Build version 13C100

• Do you have a sample that shows the issue? Yes:

  echo 'private var abc: Int { get { 123 } set() { } }' | swiftlint lint --no-cache --use-stdin --enable-all-rules`

Start by reproducing the unused_setter_value report with swiftlint lint --no-cache --use-stdin --enable-all-rules and the empty-setter sample. Trace the unused_setter_value rule and its existing examples or tests, then confirm that the empty setter no longer produces a violation while other offending cases still do.