Fixes module 'get_filesystem' error

[QasimKhan5x]

Fixes #1919

Description

The following error occurs when running the notebook in Google Colab (which has TensorFlow installed):

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
[<ipython-input-9-cff6eb059fb9>](https://localhost:8080/#) in <module>()
     16 writer.add_embedding(features,
     17                     metadata=class_labels,
---> 18                     label_img=images.unsqueeze(1))
     19 writer.flush()
     20 writer.close()

[/usr/local/lib/python3.7/dist-packages/torch/utils/tensorboard/writer.py](https://localhost:8080/#) in add_embedding(self, mat, metadata, label_img, global_step, tag, metadata_header)
    808         save_path = os.path.join(self._get_file_writer().get_logdir(), subdir)
    809 
--> 810         fs = tf.io.gfile.get_filesystem(save_path)
    811         if fs.exists(save_path):
    812             if fs.isdir(save_path):

AttributeError: module 'tensorflow._api.v2.io.gfile' has no attribute 'get_filesystem'

The proposed (temporary) fix is to add the following code:

import tensorflow as tf
import tensorboard as tb
tf.io.gfile = tb.compat.tensorflow_stub.io.gfile

I added the code and a helpful comment, but kept the code commented to ensure it only needs to be executed by users running in Colab or other TensorFlow-enabled environments. This approach avoids introducing unnecessary dependencies.

cc @aaronenyeshi @chaekit

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[svekars]

One nit, but LGMT