fix: name the output group after the module the model exposes

outputs_dataset keyed on Head:Tanh, a path of the former Python model; the config builds the model from UNetPlusPlus.yml, which exposes Tanh, so prediction failed to resolve the output group.

Finetune/Prediction.yml

@@ -89,7 +89,7 @@ Predictor:
     use_cache: false
     batch_size: 8
   outputs_dataset:
-    Head:Tanh:
+    Tanh:
       OutputDataset:
         name_class: OutSameAsGroupDataset
         before_reduction_transforms: