Changed branch-alias of dev-master to 2.1-dev (#3038)

* Update branch-alias

* Update composer.json

Author: limingxinleo

composer.json

@@ -48,7 +48,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "2.0-dev"
+            "dev-master": "2.1-dev"
         },
         "hyperf": {
             "config": "Hyperf\\WebSocketServer\\ConfigProvider"