fix span issue on tutorial index (#15279)

Author: thomelane

docs/tutorials/index.md

@@ -91,7 +91,7 @@ Select API: 
    * [Image similiarity search with InfoGAN](/tutorials/gluon/info_gan.html)
 * Practitioner Guides
     * [Gotchas using NumPy](/tutorials/gluon/gotchas_numpy_in_mxnet.html)
-    * [Multi-GPU training](/tutorials/gluon/multi_gpu.html)<span style="color:red"> (new!) ([Alternative](http://gluon.mxnet.io/chapter07_distributed-learning/multiple-gpus-gluon.html) <img src="https://upload.wikimedia.org/wikipedia/commons/6/6a/External_link_font_awesome.svg" alt="External link" height="15px" style="margin: 0px 0px 3px 3px;"/>)
+    * [Multi-GPU training](/tutorials/gluon/multi_gpu.html)<span style="color:red"> (new!) </span>([Alternative](http://gluon.mxnet.io/chapter07_distributed-learning/multiple-gpus-gluon.html) <img src="https://upload.wikimedia.org/wikipedia/commons/6/6a/External_link_font_awesome.svg" alt="External link" height="15px" style="margin: 0px 0px 3px 3px;"/>)
     * [Checkpointing and Model Serialization (a.k.a. saving and loading)](/tutorials/gluon/save_load_params.html) <img src="https://upload.wikimedia.org/wikipedia/commons/6/6a/External_link_font_awesome.svg" alt="External link" height="15px" style="margin: 0px 0px 3px 3px;"/> ([Alternative](http://gluon.mxnet.io/chapter03_deep-neural-networks/serialization.html))
     * [Distributed Training](https://github.com/apache/incubator-mxnet/tree/master/example/distributed_training)
     * [Inference using an ONNX model](/tutorials/onnx/inference_on_onnx_model.html)
@@ -101,10 +101,9 @@ Select API:&nbsp;
     * [Learning Rate Schedules](/tutorials/gluon/learning_rate_schedules.html)
     * [Advanced Learning Rate Schedules](/tutorials/gluon/learning_rate_schedules_advanced.html)
     * [Profiling MXNet Models](/tutorials/python/profiler.html)
-    * [Module to Gluon API](/tutorials/python/module_to_gluon.html)</span>
+    * [Module to Gluon API](/tutorials/python/module_to_gluon.html)
     * [Gluon end to end from training to inference](/tutorials/gluon/gluon_from_experiment_to_deployment.html)
     * [Automatic Mixed Precision in Gluon](/tutorials/amp/amp_tutorial.html)
-
 * API Guides
     * Core APIs
         * NDArray