This was originally done in commit c75b71a397,
but got reverted on this branch due to the PR (#3677) being based on the wrong
branch.
We're ready to merge this to master now, so let's make it match
release-v0.33.3.
The script recaptcha_ajax.js contains minified non-free code which
we probably cannot redistribute. Since it talks to Google servers
anyway, it is better to just download it from Google directly instead
of shipping it.
This fixes#1932.
This is because otherwise it won't get picked up by python packaging.
This also fixes the problem where the "static" folder was found if
synapse wasn't started from that directory.