[bug] multiple-forms example: missing import

[petecartwright]

👋 hello friends!

Looks like some imports were accidentally deleted in #276.

Specifically, this deleteInvitiation function is no longer imported from ~/data.server. The app still builds with npm run build, but will error when running. (see gif below)

and the corresponding error in the terminal:

To reproduce:

1. open /multiple-forms locally
2. run npm i, npm run build, npm run start
3. open the local app in your browser
4. click "Delete" on any invitation on the list
5. see the error, feel sad 😢

I'll be opening a PR shortly to fix this.