Remove extra branch alias

Author: frozzare

composer.json

@@ -29,11 +29,6 @@
     "post-install-cmd": "if [ -f vendor/bin/phpcs ]; then \"vendor/bin/phpcs\" --config-set installed_paths vendor/wp-coding-standards/wpcs; fi",
     "post-update-cmd": "if [ -f vendor/bin/phpcs ]; then \"vendor/bin/phpcs\" --config-set installed_paths vendor/wp-coding-standards/wpcs; fi"
   },
-  "extra": {
-    "branch-alias": {
-      "dev-master": "3.1-dev"
-    }
-  },
   "minimum-stability": "dev",
   "prefer-stable": true
 }