Added conflict to symplify package builder because of this error: https://github.com/Setono/SyliusPluginSkeleton/runs/1208066482?check_suite_focus=true#step:9:10

Author: loevgaard

composer.json

@@ -15,6 +15,9 @@
         "thecodingmachine/phpstan-safe-rule": "^1.0",
         "vimeo/psalm": "^3.13"
     },
+    "conflict": {
+        "symplify/package-builder": "8.3.*"
+    },
     "config": {
         "sort-packages": true
     }