fix: provider credentials load error (#16695)

api/core/tools/builtin_tool/provider.py

                 provider_yaml["credentials_for_provider"][credential_name]["name"] = credential_name
 
         credentials_schema = []
-        for credential in provider_yaml.get("credentials_for_provider", {}):
+        for credential in provider_yaml.get("credentials_for_provider", {}).values():
             credentials_schema.append(credential)
 
         super().__init__(

api/core/tools/builtin_tool/providers/webscraper/webscraper.yaml

   icon: icon.svg
   tags:
     - productivity
-credentials_for_provider: []
+credentials_for_provider: {}