www/caddy, www/caddy-custom: Fix rc(8) instructions

I had 'service enable caddy' instead of 'service caddy enable' in
caddy.in, because I get it wrong so often that I had to write a
wrapper service() function in my shell.

Ludovic submitted a patch for this 5 months ago, but it went into
the same cerebral black hole as the order of service arguments.

PR: 280127
Reported by: Ludovic Hirlimann