revise comments in qat tutorial

dygraph/tutorials/slim/quantize/image_classification/mobilenetv2_qat.py

@@ -32,7 +32,7 @@ eval_dataset = pdx.datasets.ImageNet(
 # 加载模型
 model = pdx.load_model('output/mobilenet_v2/best_model')
 
-# 量化训练
+# 在线量化
 model.quant_aware_train(
     num_epochs=5,
     train_dataset=train_dataset,

dygraph/tutorials/slim/quantize/object_detection/yolov3_qat.py

@@ -41,7 +41,7 @@ eval_dataset = pdx.datasets.VOCDetection(
 # 加载模型
 model = pdx.load_model('output/yolov3_darknet53/best_model')
 
-# 量化训练
+# 在线量化
 model.quant_aware_train(
     num_epochs=50,
     train_dataset=train_dataset,

dygraph/tutorials/slim/quantize/semantic_segmentation/unet_qat.py

@@ -39,7 +39,7 @@ eval_dataset = pdx.datasets.SegDataset(
 # 加载模型
 model = pdx.load_model('output/unet/best_model')
 
-# 量化训练
+# 在线量化
 model.quant_aware_train(
     num_epochs=5,
     train_dataset=train_dataset,