remove unrelated imports turtle

Author: dnth

icevision/models/mmdet/common/mask/single_stage/model.py

@@ -1,6 +1,5 @@
 __all__ = ["model"]
 
-from turtle import back
 from icevision.imports import *
 from mmcv import Config
 from mmdet.models import build_detector

icevision/models/mmdet/common/mask/two_stage/model.py

@@ -1,6 +1,5 @@
 __all__ = ["model"]
 
-from turtle import back
 from icevision.imports import *
 from mmcv import Config
 from mmdet.models import build_detector