Fix JSDoc such that ng build --prod with angular/cli 6.0.8 succeeds again.

src/ol/layer/Group.js

@@ -27,7 +27,7 @@ import SourceState from '../source/State.js';
  * visible.
  * @property {number} [maxResolution] The maximum resolution (exclusive) below which this layer will
  * be visible.
- * @property {(Array.<module:ol/layer/Base>|module:ol/Collection.<module:ol/layer/Base>)} [layers] Child layers.
+ * @property {Array.<module:ol/layer/Base>|module:ol/Collection.<module:ol/layer/Base>} [layers] Child layers.
  */
 
 

src/ol/layer/VectorTile.js

@@ -80,7 +80,7 @@ export const RenderType = {
  * means no preloading.
  * @property {module:ol/render~OrderFunction} [renderOrder] Render order. Function to be used when sorting
  * features before rendering. By default features are drawn in the order that they are created.
- * @property {(module:ol/style/Style|Array.<module:ol/style/Style>|module:ol/style/Style~StyleFunction)} [style] Layer style. See
+ * @property {module:ol/style/Style|Array.<module:ol/style/Style>|module:ol/style/Style~StyleFunction} [style] Layer style. See
  * {@link module:ol/style} for default style which will be used if this is not defined.
  * @property {boolean} [useInterimTilesOnError=true] Use interim tiles on error.
  */