Update tensorflow package version in prereqs

to match the verison used by IREE: https://github.com/openxla/iree/blob/main/integrations/tensorflow/test/requirements.txt

Change-Id: I7813e717dd13fa7145b8683aa69abdc5e7ce9ef1

python-requirements.txt

diff --git a/python-requirements.txt b/python-requirements.txt
index d6fc26c..b4e5bfa 100644
--- a/python-requirements.txt
+++ b/python-requirements.txt
@@ -35,7 +35,7 @@
 sel4-deps
 setuptools
 tempita
-# TODO(lundong): Update to tensorflow 2.13.0 when it is released
-tf-nightly==2.13.0.dev20230501
+# TODO(lundong): not pin nightly after TOSA features are in release ver.
+tf-nightly==2.14.0.dev20230519
 wget
 yapf