Correct dev-master alias.

To allow for versions like 1.2.0 as well, the branch alias for `dev-master` needs to be changed from `1.0.x-dev` to `1.x-dev`.

Author: schlessera

composer.json

@@ -31,7 +31,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "1.0.x-dev"
+            "dev-master": "1.x-dev"
         },
         "commands": [
             "search-replace"