switches :acme to the LetsEncrypt production url
::
=/ directory-base=purl
=- (need (de-purl:html -))
- 'https://acme-staging-v02.api.letsencrypt.org/directory'
+ 'https://acme-v02.api.letsencrypt.org/directory'
:: mov: list of outgoing moves for the current transaction
::
=| mov=(list move)
