Fix: made JSON valid-ish.

[dblock]

The example JSON is not valid JSON, missing a few quotes and commas.

This is related to https://github.com/slackhq/slack-api-docs/issues/37.

[dblock]

@paulhammond Thanks for synching this repo. Can you apply this in your internal repo please? Trying to do some scrape/parsing for types in https://github.com/dblock/slack-api-ref and it's breaking in silly ways.

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