Fix cod in API doc of pruning. (#836)

docs/zh_cn/api_cn/dygraph/pruners/l1norm_filter_pruner.rst

@@ -28,7 +28,7 @@ L1NormFilterPruner
     from paddleslim import L1NormFilterPruner
     net = mobilenet_v1(pretrained=False) 
     pruner = L1NormFilterPruner(net, [1, 3, 224, 224])
-    pruner.prune_var("conv2d_26.w_0", [0], pruned_ratio=0.5)
+    pruner.prune_var("conv2d_26.w_0", [0], 0.5)
     optimizer = paddle.optimizer.Momentum(
         learning_rate=0.1,
         parameters=net.parameters())
@@ -79,7 +79,7 @@ L1NormFilterPruner
       from paddleslim import L1NormFilterPruner
       net = mobilenet_v1(pretrained=False) 
       pruner = L1NormFilterPruner(net, [1, 3, 224, 224])
-      plan = pruner.prune_var("conv2d_26.w_0", [0])
+      plan = pruner.prune_var("conv2d_26.w_0", [0], 0.5)
       print(f"plan: {plan}")
       paddle.summary(net, (1, 3, 224, 224))
    ..