Update SummaryBox doc

[JingyuZ]

didn't test in storybook, but when actually using it,, the syntax would be: <SummaryBox items={[{value: "Alpha", label: "Bravo"}, {value: "Charlie Brown", label: "Delta"}, {value: "Echo"}, …]} /> instead of {{...}}

[gthomas-appfolio]

Yes, sorry this is some weird storybook parsing issue, not sure if we can fix in docs