Remove absl test and logging deps from Python unit tests. (#9069)

This has been bugging me for a while because it adds no value and requires more deps to be installed.

Does not touch integrations/tensorflow since installing TF pulls absl-py along for the ride.
diff --git a/samples/colab/test_notebooks.py b/samples/colab/test_notebooks.py
index 7e5632c..4e7d307 100644
--- a/samples/colab/test_notebooks.py
+++ b/samples/colab/test_notebooks.py
@@ -5,12 +5,11 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 import glob
+import logging
 import os
 import subprocess
 import unittest
 
-from absl.testing import absltest
-
 NOTEBOOKS_TO_SKIP = []
 
 NOTEBOOKS_EXPECTED_TO_FAIL = [
@@ -18,7 +17,7 @@
 ]
 
 
-class ColabNotebookTests(absltest.TestCase):
+class ColabNotebookTests(unittest.TestCase):
   """Tests running all Colab notebooks in this directory."""
 
   @classmethod
@@ -50,4 +49,5 @@
 
 if __name__ == "__main__":
   ColabNotebookTests.generateTests()
-  absltest.main()
+  logging.basicConfig(level=logging.DEBUG)
+  unittest.main()