Fix unique key issue in new event summary page

[Arnei]

Fixes a web console complaint about missing unique keys in the summary page for new events and series, which could have potentially caused bugs if you were jumping between tabs and making changes a lot.

[KatrinIhler]

I'm (maybe wrongfully) assuming that this references this error:

Warning: Each child in a list should have a unique "key" prop.
Check the render method of WizardStepperEvent. See https://reactjs.org/link/warning-keys for more information.
WizardStepperEvent@http://localhost:3000/admin-ui/static/js/bundle.js:45873:28
ConnectFunction@http://localhost:3000/admin-ui/static/js/bundle.js:249167:68
Formik@http://localhost:3000/admin-ui/static/js/bundle.js:148704:28
NewEventWizard@http://localhost:3000/admin-ui/static/js/bundle.js:33393:24
section
NewResourceModal@http://localhost:3000/admin-ui/static/js/bundle.js:38271:26
section
Events@http://localhost:3000/admin-ui/static/js/bundle.js:12464:16
ConnectFunction@http://localhost:3000/admin-ui/static/js/bundle.js:249167:68
RenderedRoute@http://localhost:3000/admin-ui/static/js/bundle.js:253446:7
Routes@http://localhost:3000/admin-ui/static/js/bundle.js:254136:7
Router@http://localhost:3000/admin-ui/static/js/bundle.js:254075:7
HashRouter@http://localhost:3000/admin-ui/static/js/bundle.js:252087:7
App@http://localhost:3000/admin-ui/static/js/bundle.js:8375:75
LocalizationProvider@http://localhost:3000/admin-ui/static/js/bundle.js:105792:9
ThemeProvider@http://localhost:3000/admin-ui/static/js/bundle.js:94075:7
ThemeProvider@http://localhost:3000/admin-ui/static/js/bundle.js:95267:7
ThemeProvider@http://localhost:3000/admin-ui/static/js/bundle.js:92655:9
PersistGate@http://localhost:3000/admin-ui/static/js/bundle.js:265354:20
Provider@http://localhost:3000/admin-ui/static/js/bundle.js:248909:15

that pops up in the web console when opening the event details? If so, I'm still seeing that one. 🤔

[ziegenberg]

@KatrinIhler the error you found should be solved by #386.