Exhaustive deps warning in AutcompleteTagInputExample

[brandongregoryscott]

Looks like the way we've written this example is giving an exhaustive deps warning. Open the CodeSandbox at https://evergreen.segment.com/components/tag-input#autocomplete and click on the Problems panel to see:

I think we can move allValues outside of the function scope so it isn't redefined every render to resolve this warning.