Deprecate SequenceFile Dataset (#415)
Deprecate SequenceFile Dataset (#415)

SequenceFile Dataset was never in good use,
and the trend of industry aggressively switching from
self-managed Hadoop system to cloud-vendor provided storage (S3/GCS/etc)
makes this Dataset format less and less relevant.
This PR deprecates SequenceFile Dataset

Signed-off-by: Yong Tang <765086fe2e0c1f980161f127fec596800f327f62@outlook.com>
tensorflow/io,tensorflow/io,tensorflow/io,tensorflow/io,tensorflow/io,tensorflow/io,tensorflow/io