Master is not 4.x (see getsentry#337)

Author: Jean85

composer.json

@@ -67,7 +67,7 @@
     },
     "extra": {
         "branch-alias": {
-            "master": "3.x-dev",
+            "master": "4.x-dev",
             "releases/3.2.x": "3.2.x-dev",
             "releases/2.x": "2.x-dev",
             "releases/1.x": "1.x-dev"