[token-server] Bump recaptcha score

Summary:
We took this from 0.7 to 0.5 in D17807

This was motivated by reports of false positives. In testing tho, it seems like "tests are too strict" is expected behavior for incognito mode.

Try 0.8 as there is currently someone using some kind of scripted claiming on the XEC faucet, will see if this prevents.

Test Plan:
npm test

after landing, check out https://explorer.e.cash/address/ecash:qrk9q5g26ejy6jsqnz4kjnavdy9ra47ycyt36q9lxc

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17875