Ping TF to 2.5.0rc1 (#1386)
Ping TF to 2.5.0rc1 (#1386)

as was discussed in https://github.com/tensorflow/io/pull/1382#issuecomment-828921097

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