Pin Keras 2 for new TF versions

setup.py

@@ -1,6 +1,6 @@
 import setuptools
 
-tensorflow = ["tensorflow>=2.6"]
+tensorflow = ["tensorflow>=2.6" "tf-keras~=2.16"]
 pytorch = ["torch>=1.11", "torchdata"]
 sklearn = ["scikit-learn>=1.0"]
 cloud = ["tiledb-cloud"]

tiledb/ml/__init__.py

@@ -4,6 +4,9 @@
 #  https://pypi.org/project/setuptools-scm/#:~:text=Retrieving%20package%20version%20at%20runtime, when we stop
 #  supporting Python 3.7. We the aforementioned change, we can avoid the 100ms overhead during import of the package.
 
+import os
+os.environ["TF_USE_LEGACY_KERAS"] = 1
+
 try:
     __version__ = get_distribution("tiledb-ml").version
 except DistributionNotFound: