Remove Tensorflow version constraint in developer dependencies

[elisno]

#1052 needs to be reverted when we can run the unit tests on Tensorflow 2.16+

See these lines:

cleanlab/requirements-dev.txt

Line 14 in 589edd6

tensorflow<2.16

cleanlab/.github/workflows/ci.yml

Line 34 in 589edd6

pip install tensorflow-cpu<2.16

Just drop the <2.16 and verify that CI installs 2.16 in this environment and passes the unit tests for Ubuntu, macOs and Windows.