Bump branch-alias to 5.2

Author: nicolas-grekas

composer.json

@@ -84,11 +84,11 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "5.1-dev"
+            "dev-master": "5.2-dev"
         },
         "symfony": {
             "allow-contrib": false,
-            "require": "5.1.*"
+            "require": "5.2.*"
         }
     }
 }