fix image colorization model load issue

之前的评审提交（https://code.alibaba-inc.com/Ali-MaaS/MaaS-lib/codereview/13669766?tab=changes）可能导致 modelscope hub 的模型无法读取，对于不同 modelscope 版本使用者产生兼容性问题，因此在上次评审提交的基础上做一定修改确保兼容性。
Link: https://code.alibaba-inc.com/Ali-MaaS/MaaS-lib/codereview/13716448
* fix image colorization model load issue

modelscope/models/cv/image_colorization/ddcolor/ddcolor.py

@@ -158,7 +158,7 @@ class Encoder(nn.Module):
         return hooks
 
     def forward(self, img):
-        return self.arch(img)
+        return self.arch.forward_features(img)
 
 
 class MultiScaleColorDecoder(nn.Module):

modelscope/models/cv/image_colorization/ddcolor/utils/convnext.py

@@ -116,7 +116,7 @@ class ConvNeXt(nn.Module):
             self.add_module(layer_name, layer)
 
         self.norm = nn.LayerNorm(dims[-1], eps=1e-6)  # final norm layer
-        # self.head_cls = nn.Linear(dims[-1], 4)
+        self.head_cls = nn.Linear(dims[-1], 4)
 
         self.apply(self._init_weights)
         # self.head_cls.weight.data.mul_(head_init_scale)
@@ -141,7 +141,7 @@ class ConvNeXt(nn.Module):
 
     def forward(self, x):
         x = self.forward_features(x)
-        # x = self.head_cls(x)
+        x = self.head_cls(x)
         return x