Fix proxy plugin config validation

Proxy plugins are keyed only on the identifier, the type
is specified within the proxy plugin configuration which
maps to the full URI. The proxy plugin configuration is
not passed to the plugin for configuration like other
plugins.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

services/server/config/config.go

@@ -107,11 +107,6 @@ func (c *Config) ValidateV2() error {
 			return errors.Errorf("invalid plugin key URI %q expect io.containerd.x.vx", p)
 		}
 	}
-	for p := range c.ProxyPlugins {
-		if len(strings.Split(p, ".")) < 4 {
-			return errors.Errorf("invalid proxy plugin key URI %q expect io.containerd.x.vx", p)
-		}
-	}
 	return nil
 }