rn,tracks: fix loadEffects

The resolved promise is expected to return an array.

react/features/base/tracks/loadEffects.native.js

  * Loads the enabled stream effects.
  *
  * @param {Object} store - The Redux store.
- * @returns {Promsie} - A Promise which resolves when all effects are created.
+ * @returns {Promsie} - A Promise which resolves with an array of the loaded effects.
  */
-export default function loadEffects(store: Object): Promise<any> { // eslint-disable-line no-unused-vars
-    return Promise.resolve();
+export default function loadEffects(store: Object): Promise<Array<any>> { // eslint-disable-line no-unused-vars
+    return Promise.resolve([]);
 }