publish: Allow slash '/' character in distribution name on publishing

There's no apparent reason to disallow this type of characters in the
distribution name. Aptly will just create the proper subdirectories to
that path.

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>

deb/publish.go

@@ -264,10 +264,6 @@ func NewPublishedRepo(storage, prefix, distribution string, architectures []stri
 		}
 	}
 
-	if strings.Contains(distribution, "/") {
-		return nil, fmt.Errorf("invalid distribution %s, '/' is not allowed", distribution)
-	}
-
 	result.Distribution = distribution
 
 	// only fields which are unique by all given snapshots are set on published