fix: Use Result.fail for a failed migration callback in the sync contract service

Author: jsonbailey

contract-tests/client_entity.py

@@ -265,7 +265,7 @@ def fn(payload) -> Result:
                 if response.status_code == 200:
                     return Result.success(response.text)
 
-                return Result.error(f"Request failed with status code {response.status_code}")
+                return Result.fail(f"Request failed with status code {response.status_code}")
 
             return fn