add runtime shape for fuse_emb_seq_pool_grad

test=develop

paddle/fluid/operators/fused/fused_embedding_seq_pool_op.h

@@ -121,6 +121,8 @@ class FusedEmbeddingSeqPoolGradKernel : public framework::OpKernel<T> {
       auto *ids = context.Input<LoDTensor>("Ids");
       auto *d_output = context.Input<LoDTensor>(framework::GradVarName("Out"));
       auto *d_table = context.Output<SelectedRows>(framework::GradVarName("W"));
+      // runtime shape
+      d_table->set_height(table_dim[0]);
 
       auto *ids_data = ids->data<int64_t>();
       int64_t ids_num = ids->numel();