Pin TensorFlow nightly version to make integration tests hermetic.
Pin TensorFlow nightly version to make integration tests hermetic.

We'll bump this ~weekly to keep track of TF2 progress.

PiperOrigin-RevId: 248693469
Change-Id: Id2861f9f4df8a27c1784c26c0769ebdb61d46922

deepmind/sonnet,deepmind/sonnet