Update version.py to 1.0.3

Let TF-GNN support TF2.16+ via `TF_USE_LEGACY_KERAS=1`.

PiperOrigin-RevId: 619267380

Update version.py to 1.0.2

Switch tensorflow_gnn/experimental/sampler/eval_dag.py to tf_internal.py

for dealing with internals of different Keras versions.

PiperOrigin-RevId: 604655724

Let TF-GNN choose between keras or tf_keras consistently with TF 2.15:

both provide Keras 2.15, but it matters which one is used,
because they have separate class hierarchies and global registries.

Along the way, refactor the nested case distinctions of tf_internal.py
into a clear list of supported older TF/Keras versions.

PiperOrigin-RevId: 604619976

Fix passing through the reduce_type in graph regression tasks

PiperOrigin-RevId: 594226366

Revert change to setup.py with mistletoe, breaking install from sdist.

This reverts commit 500bcc2.

Update version.py to 1.0.0rc0

Cleanup old sampler examples.

PiperOrigin-RevId: 590617039

Update version.py to 0.6.1.