key prefix of python-setuptools mismatch in PUBLIC_dependencies.txt and Dockerfile-ubuntu_cb_nullworkload

[rayx]

configs/templates/PUBLIC_dependencies.txt uses python prefix for keys of python-setuptools. However, docker/workload/Dockerfile-ubuntu_cb_nullworkload uses python3 prefix for keys of python-setuptools. The mismatch leads to the following error when running install script. The error causes install script abort without installing all required dependencies.

[2024-07-08 06:11:43,078] [ERROR] dependencies.py/get_cmdline  - ######## Error! The command to  install the dependency python-setuptools is empty!

Fix: modify Dockerfile-ubuntu_cb_nullworkload as below:

# python-setuptools-install-pip
RUN pip3 install --upgrade setuptools
# python-setuptools-install-pip