fix lenet num classes (#28642)

python/paddle/vision/models/lenet.py

@@ -49,7 +49,8 @@ class LeNet(nn.Layer):
 
         if num_classes > 0:
             self.fc = nn.Sequential(
-                nn.Linear(400, 120), nn.Linear(120, 84), nn.Linear(84, 10))
+                nn.Linear(400, 120),
+                nn.Linear(120, 84), nn.Linear(84, num_classes))
 
     def forward(self, inputs):
         x = self.features(inputs)