reCAPTCHA field doesn't show on Safari and Chrome for users in China.

Description amended to add:

As described in the linked issue MDLSITE-3878, the reCAPTCHA used on moodle.org was updated recently. The change didn't seem to have any affect on spammer account creation. As it's now blocking users in China from creating accounts, please could we revert the reCAPTCHA used i.e. go back to using the old one.