[Housekeeping] Refactor `Checkbox used in list` example to comply with `ion-checbox`

[jakobe]

• [x] I have written a good issue

Describe the housekeeping request

We are currently using ion-checkbox in a deprecated way regarding labels in Checkbox used in a list

Refactor Checkbox used in a list example to use ion-checkbox with a label in it's default slot.

Read more: https://ionicframework.com/docs/api/checkbox#migrating-from-legacy-checkbox-syntax

Have you considered any alternatives?

We could use the legacy option, but this will also be removed in future version of Ionic:

Developers can use the "legacy" property to continue using the legacy form markup. This property will be removed in an upcoming major release of Ionic where this form control will use the modern form markup.

Are there any additional context?

No.