Don't remove if there is `methodName=` name

[xuwei-k]

class D2 {
  def +++(d: D2): D2 = this // don't remove!
}

object D2 {
  def main(args: Array[String]): Unit = {
    var d = new D2
    d +++= d
  }
}

• https://github.com/xuwei-k/unused-code/commit/5ece18d9ea93eb35f1c421f850a5c30908ea1c61
• https://github.com/xuwei-k/unused-code/runs/5263110515?check_suite_focus=true