Use ion-item in collection repeat demo

On slide 30, demonstrating complex lists, you make use of ion-item. Then on slide 31 showing collection-repeat, you revert back to a div with a class. This works of course, but I think it is better to be consistent and use the directive version. Plus it is pretty impressive to point out how you can go from a 'normal' list to a better performing one with one tiny edit.

Compare the complex-list example on slide 30 with the collection-repeat example on slide 31. Update the latter to use the directive version consistently, then review the presentation to confirm the example still demonstrates collection-repeat and the intended performance comparison.

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