Outbound: One endpoint and at most one user only (#5144)

https://github.com/XTLS/Xray-core/pull/5124#issuecomment-3281091009

Fixes https://github.com/XTLS/Xray-core/pull/5124#pullrequestreview-3218097421

proxy/vmess/inbound/config.proto

@@ -19,6 +19,4 @@ message DefaultConfig {
 message Config {
   repeated xray.common.protocol.User user = 1;
   DefaultConfig default = 2;
-  DetourConfig detour = 3;
-  // 4 is for legacy setting
 }