chore: update plugin requires

Author: ruibaby

src/main/resources/plugin.yaml

@@ -8,7 +8,7 @@ metadata:
     "store.halo.run/app-id": "app-YXyaD"
 spec:
   enabled: true
-  requires: ">=2.14.0"
+  requires: ">=2.15.0"
   author:
     name: Halo OSS Team
     website: https://github.com/halo-dev