fix(docs): fix remove chip in chips autocomplete example

[CodySchaaf]

The output is removed not remove https://github.com/angular/material2/blob/master/src/lib/chips/chip.ts#L209

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[CodySchaaf]

I signed it!

[googlebot]

CLAs look good, thanks!

[crisbeto]

Thank you for the PR, however it'll have to be closed, because there's a pending PR that fixes the issue already: #11175.

[CodySchaaf]

Ah my searching didn't pull anything up, thanks for finding. 👍

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