!16117 modfy fcn8s readme

From: @wukesong
Reviewed-by: @liangchenghui,@wuxuejian
Signed-off-by: @liangchenghui,@wuxuejian

model_zoo/official/cv/FCN8s/README.md

@@ -204,7 +204,7 @@ For more information, see `config.py`.
 | Dataset             | PASCAL VOC 2012
 | batch_size          | 16
 | outputs             | probability
-| mean IoU            | 64.25
+| mean IoU            | 0.627
 
 # [Description of Random Situation](#contents)
 

model_zoo/official/cv/FCN8s/README_CN.md

@@ -202,7 +202,7 @@ FCN8s使用丢弃全连接操作的VGG16作为编码部分，并分别融合VGG1
 | 数据集             | PASCAL VOC 2012
 | 批大小          | 16
 | 输出             | 概率
-| 平均 IoU            | 64.25
+| 平均 IoU            | 0.627
 
 # [随机事件介绍](#目录)