Fix comments in framework (#32861)

* Fix comments in framework

* Update framework.py

python/paddle/framework/framework.py

@@ -96,11 +96,12 @@ def set_grad_enabled(mode):
 
     Examples:
         .. code-block:: python
+            import paddle
             x = paddle.ones([3, 2])
             x.stop_gradient = False
-            with torch.set_grad_enabled(False):
+            with paddle.set_grad_enabled(False):
                 y = x * 2
-                with torch.set_grad_enabled(True):
+                with paddle.set_grad_enabled(True):
                     z = x * 2
             print(y.stop_gradient)   # True
             print(z.stop_gradient)   # False