[fbsync] remove unused package in coco_eval.py (#4404)

Reviewed By: datumbox

Differential Revision: D31268027

fbshipit-source-id: f83d609de41e3954513b05dda7125b30d615fb2f

Author: NicolasHug

references/detection/coco_eval.py

@@ -1,9 +1,7 @@
 import json
-import tempfile
 
 import numpy as np
 import copy
-import time
 import torch
 import torch._six