docs(store): add missing comma to createFeature example (#4972)

Author: DavidGoestemeier

modules/store/src/feature_creator.ts

@@ -138,10 +138,10 @@ export function createFeature<FeatureName extends string, FeatureState>(
  *   name: 'products',
  *   reducer: createReducer(
  *     initialState,
- *     on(ProductsApiActions.loadSuccess(state, { products }) => ({
+ *     on(ProductsApiActions.loadSuccess, (state, { products }) => ({
  *       ...state,
  *       products,
- *     }),
+ *     })),
  *   ),
  * });
  *