Update branch-alias to 5.1.x-dev (#293)

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: github-actions[bot]

composer.json

@@ -43,7 +43,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-main": "5.0.x-dev"
+            "dev-main": "5.1.x-dev"
         },
         "phpstan": {
             "includes": [