r/dch-yum: Explicitly disable proxy for repo

*unifi1.pyrocufflink.blue* requires a proxy to access Yum repositories
on the Internet, so it has the `proxy` setting configured globally.  The
proxy does NOT allow access to internal resources, however.  The
internal repository is directly accessible by that machine, so it needs
to be configured thus.

roles/dch-yum/files/dch.repo

@@ -4,3 +4,4 @@ baseurl=https://files.pyrocufflink.blue/yum/dch/fedora/$releasever
 gpgkey=https://files.pyrocufflink.blue/yum/dch/gnupg.pub
 gpgcheck=1
 skip_if_unavailable=true
+proxy=_none_