Fix incorrect CLI commands in Datasets Docs (#14889)

docs/en/datasets/classify/mnist.md

@@ -52,7 +52,7 @@ To train a CNN model on the MNIST dataset for 100 epochs with an image size of 3
 
         ```bash
         # Start training from a pretrained *.pt model
-        cnn detect train data=mnist model=yolov8n-cls.pt epochs=100 imgsz=28
+        yolo classify train data=mnist model=yolov8n-cls.pt epochs=100 imgsz=28
         ```
 
 ## Sample Images and Annotations
@@ -113,7 +113,7 @@ To train a model on the MNIST dataset using Ultralytics YOLO, you can follow the
     
         ```bash
         # Start training from a pretrained *.pt model
-        cnn detect train data=mnist model=yolov8n-cls.pt epochs=100 imgsz=28
+        yolo classify train data=mnist model=yolov8n-cls.pt epochs=100 imgsz=28
         ```
 
 For a detailed list of available training arguments, refer to the [Training](../../modes/train.md) page.