Fix exception when opening timepicker

[Arnei]

If you open a time picker (e.g. "startDate" in the event details), the ui crashes with an exception:
"Format string contains an unescaped latin alphabet character n ".

This fixes that by downgrading the date-fns dependency. Allegedly the issues is with material-ui not providing the correct types for date-fns, but downgrading material-ui would cause more problems.

[gregorydlogan]

I get the following when doing the final submit for scheduling an event

Uncaught runtime errors:
ERROR
Invariant failed: A state mutation was detected between dispatches, in the path 'workflows.workflows.1.configuration_panel_json.0.fieldset.0.value'.  This may cause incorrect behavior. (https://redux.js.org/style-guide/style-guide#do-not-mutate-state)
invariant@http://localhost:3000/admin-ui/static/js/bundle.js:101231:9
./node_modules/@reduxjs/toolkit/dist/redux-toolkit.esm.js/createImmutableStateInvariantMiddleware/</</</<@http://localhost:3000/admin-ui/static/js/bundle.js:101374:20
measureTime@http://localhost:3000/admin-ui/static/js/bundle.js:101131:16
./node_modules/@reduxjs/toolkit/dist/redux-toolkit.esm.js/createImmutableStateInvariantMiddleware/</</<@http://localhost:3000/admin-ui/static/js/bundle.js:101370:22
./node_modules/@reduxjs/toolkit/dist/redux-toolkit.esm.js/createActionCreatorInvariantMiddleware/</</<@http://localhost:3000/admin-ui/static/js/bundle.js:101118:16
checkAcls@http://localhost:3000/admin-ui/static/js/bundle.js:28506:30
onClick@http://localhost:3000/admin-ui/static/js/bundle.js:28455:21
callCallback@http://localhost:3000/admin-ui/static/js/bundle.js:170821:18
invokeGuardedCallbackDev@http://localhost:3000/admin-ui/static/js/bundle.js:170865:20
invokeGuardedCallback@http://localhost:3000/admin-ui/static/js/bundle.js:170920:35
invokeGuardedCallbackAndCatchFirstError@http://localhost:3000/admin-ui/static/js/bundle.js:170934:29
executeDispatch@http://localhost:3000/admin-ui/static/js/bundle.js:174556:46
processDispatchQueueItemsInOrder@http://localhost:3000/admin-ui/static/js/bundle.js:174582:26
processDispatchQueue@http://localhost:3000/admin-ui/static/js/bundle.js:174593:41
dispatchEventsForPlugins@http://localhost:3000/admin-ui/static/js/bundle.js:174602:27
./node_modules/react-dom/cjs/react-dom.development.js/dispatchEventForPluginEventSystem/<@http://localhost:3000/admin-ui/static/js/bundle.js:174780:16
batchedEventUpdates$1@http://localhost:3000/admin-ui/static/js/bundle.js:186602:16
batchedEventUpdates@http://localhost:3000/admin-ui/static/js/bundle.js:170644:16
dispatchEventForPluginEventSystem@http://localhost:3000/admin-ui/static/js/bundle.js:174779:26
attemptToDispatchEvent@http://localhost:3000/admin-ui/static/js/bundle.js:172568:40
dispatchEvent@http://localhost:3000/admin-ui/static/js/bundle.js:172501:45
unstable_runWithPriority@http://localhost:3000/admin-ui/static/js/bundle.js:243997:16
runWithPriority$1@http://localhost:3000/admin-ui/static/js/bundle.js:177157:14
discreteUpdates$1@http://localhost:3000/admin-ui/static/js/bundle.js:186617:18
discreteUpdates@http://localhost:3000/admin-ui/static/js/bundle.js:170654:16
dispatchDiscreteEvent@http://localhost:3000/admin-ui/static/js/bundle.js:172471:22

[Arnei]

Does not appear for me, although that might be because I only tested it after merging the main branch into this one. Could you clear your browser cache and test again?