Remove remaining use of inherits in src

src/ol/source/Source.js

@@ -37,24 +37,24 @@ import SourceState from '../source/State.js';
  */
 
 
-/**
- * @classdesc
- * Abstract base class; normally only used for creating subclasses and not
- * instantiated in apps.
- * Base class for {@link module:ol/layer/Layer~Layer} sources.
- *
- * A generic `change` event is triggered when the state of the source changes.
- *
- * @constructor
- * @abstract
- * @extends {module:ol/Object}
- * @param {module:ol/source/Source~Options} options Source options.
- * @api
- */
-class Source {
+class Source extends BaseObject {
+  /**
+   * @classdesc
+   * Abstract base class; normally only used for creating subclasses and not
+   * instantiated in apps.
+   * Base class for {@link module:ol/layer/Layer~Layer} sources.
+   *
+   * A generic `change` event is triggered when the state of the source changes.
+   *
+   * @constructor
+   * @abstract
+   * @extends {module:ol/Object}
+   * @param {module:ol/source/Source~Options} options Source options.
+   * @api
+   */
   constructor(options) {
 
-    BaseObject.call(this);
+    super();
 
     /**
     * @private
@@ -177,8 +177,6 @@ class Source {
   }
 }
 
-inherits(Source, BaseObject);
-
 /**
  * @param {module:ol/coordinate~Coordinate} coordinate Coordinate.
  * @param {number} resolution Resolution.