software/rapid-cdn: Use curl with http3 by default

It's very usefuly to have access to such powerful tool on each CDN node, and
we shall eat our dog food anyway.

software/rapid-cdn/software.cfg

@@ -107,8 +107,7 @@ nginx_mime = ${nginx-output:mime}
 haproxy_executable = ${haproxy:location}/sbin/haproxy
 haproxy_quic_executable = ${haproxy-quic:location}/sbin/haproxy
 rsyslogd_executable = ${rsyslogd:location}/sbin/rsyslogd
-curl = ${curl:location}
-curl_http3 = ${curl-http3:location}
+curl = ${curl-http3:location}
 dash = ${dash:location}
 gzip = ${gzip:location}
 logrotate = ${logrotate:location}