Remove tf.compat.v1 imports in granite/

No API changes were needed here.

Reviewers: ondrasej, orodley, virajbshah

Reviewed By: ondrasej

Pull Request: #331

Author: boomanaiden154

gematria/granite/python/gnn_model_base.py

@@ -26,8 +26,7 @@
 from gematria.model.python import options
 import graph_nets
 import sonnet as snt
-import tensorflow.compat.v1 as tf
-import tensorflow as tf2
+import tensorflow as tf
 import tf_keras