MNT Remove obsolete branch-alias

composer.json

@@ -2,7 +2,11 @@
     "name": "silverstripe/widgets",
     "description": "Widgets are small pieces of functionality such as showing the latest Comments or Flickr Photos. They normally display on the sidebar of your website.",
     "type": "silverstripe-vendormodule",
-    "keywords": ["silverstripe", "widgets", "blog"],
+    "keywords": [
+        "silverstripe",
+        "widgets",
+        "blog"
+    ],
     "authors": [
         {
             "name": "Ingo Schommer",
@@ -20,9 +24,6 @@
         "squizlabs/php_codesniffer": "^3.0"
     },
     "extra": {
-        "branch-alias": {
-            "dev-master": "2.x-dev"
-        },
         "expose": [
             "css",
             "javascript"
@@ -37,4 +38,4 @@
     "license": "BSD-3-Clause",
     "minimum-stability": "dev",
     "prefer-stable": true
-}
+}