Remove remaining use of inherits in src

src/ol/structs/LRUCache.js

@@ -16,22 +16,22 @@ import EventType from '../events/EventType.js';
  */
 
 
-/**
- * Implements a Least-Recently-Used cache where the keys do not conflict with
- * Object's properties (e.g. 'hasOwnProperty' is not allowed as a key). Expiring
- * items from the cache is the responsibility of the user.
- * @constructor
- * @extends {module:ol/events/EventTarget}
- * @fires module:ol/events/Event~Event
- * @struct
- * @template T
- * @param {number=} opt_highWaterMark High water mark.
- */
-class LRUCache {
+class LRUCache extends EventTarget {
 
+  /**
+   * Implements a Least-Recently-Used cache where the keys do not conflict with
+   * Object's properties (e.g. 'hasOwnProperty' is not allowed as a key). Expiring
+   * items from the cache is the responsibility of the user.
+   * @constructor
+   * @extends {module:ol/events/EventTarget}
+   * @fires module:ol/events/Event~Event
+   * @struct
+   * @template T
+   * @param {number=} opt_highWaterMark High water mark.
+   */
   constructor(opt_highWaterMark) {
 
-    EventTarget.call(this);
+    super();
 
     /**
      * @type {number}
@@ -298,6 +298,4 @@ class LRUCache {
 
 }
 
-inherits(LRUCache, EventTarget);
-
 export default LRUCache;