Update setup.py

Author: vkarampudi

setup.py

@@ -225,7 +225,7 @@ def select_constraint(default, nightly=None, git_master=None):
         ),
         "tfx-bsl"
         + select_constraint(
-            default="@git+https://github.com/tensorflow/tfx-bsl@master",
+            default="@git+https://github.com/tensorflow/tfx-bsl@testing",
             nightly=">=1.18.0.dev",
             git_master="@git+https://github.com/tensorflow/tfx-bsl@master",
         ),