message: doc: Fix usage
diff: @@ -12,11 +12,11 @@ let reference = {};
  const detector = new LeakDetector(reference);
  // Reference is held in memory.
  -console.log(detector.isLeaked()); // true
  +console.log(detector.isLeaking()); // true
  // We destroy the only reference to the object.
  reference = null;
  // Reference is gone.
  -console.log(detector.isLeaked()); // false
  +console.log(detector.isLeaking()); // false
  ```
  