Properly use useAppDispatch hook

Function call parentheses were accidentally removed in
3e77a0a.

The code is only invoked during runtime when accessing the narrative
editor, which was not tested before merging that change.

src/components/narrativeEditor/useDatasetFetch.js

@@ -14,7 +14,7 @@ import { FetchError } from "../../util/exceptions";
  */
 
 export function useDatasetFetch(datasets) {
-  const dispatchRedux = useAppDispatch;
+  const dispatchRedux = useAppDispatch();
   const [datasetResponses, dispatchDatasetResponses] = useReducer(
     (state, action) => {
       if (action.reset) return {};