[Eager] Fix sharding in eager (#44271)

* fix sharding in eager

* support eager sharding

python/paddle/distributed/fleet/meta_parallel/sharding/group_sharded_stage2.py

@@ -210,6 +210,7 @@ class GroupShardedStage2(nn.Layer):
                     scale=self._world_size_scaling)
 
         # Scale grads of params
+        with paddle.no_grad():
             for param in self._trainable_params:
                 if param.name in self._param_grads and param.grad is not None:
                     param.grad.scale_(scale=self._world_size_scaling)