[token-server] Bump claim xec rate limit

Summary:
With recaptcha implemented, no longer seeing scripted attacks.

It's possible to get denied by recaptcha if you happen to be a preternaturally-fast-clicking human. In this event, blocking all further claims for a week is a bit draconian.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16930