Fix eval.py source path in task configuration

Updated the source path for eval.py in task.yml.

Author: Mark Saroufim

problems/nvidia/nvfp4_group_gemm/task.yml

@@ -5,7 +5,7 @@ files:
   - {"name": "task.py", "source": "task.py"}
   - {"name": "utils.py", "source": "utils.py"}
   - {"name": "reference.py", "source": "reference.py"}
-  - {"name": "eval.py", "source": "../eval.py"}
+  - {"name": "eval.py", "source": "eval.py"}
 
 lang: "py"