Revert "[AutoParallel] use inplace multiply in grad_clip (PaddlePaddle#71421)"

This reverts commit 9fee57d.

Author: Waynezee

python/paddle/nn/clip.py

@@ -840,12 +840,8 @@ def async_add_n(var_list):
                         clip_input = paddle.distributed.reshard(
                             clip_input, g.process_mesh, clip_input.placements
                         )
-                if g.is_dist() or g.is_dense():
-                    g.multiply_(clip_input)
-                    params_and_grads.append((p, g))
-                else:
-                    new_grad = paddle.multiply(g, clip_input)
-                    params_and_grads.append((p, new_grad))
+                new_grad = paddle.multiply(g, clip_input)
+                params_and_grads.append((p, new_grad))
             else:
                 params_and_grads.append((p, g))