ppx_deriving_rpc: update url
ppx_deriving_rpc: update url

Signed-off-by: Marcello Seri <34fd14c67154e888f6587d5c0e7eadd13aaf7ca7@citrix.com>

lindig/xs-opam,xapi-project/xs-opam,mseri/xs-opam,mseri/xs-opam