tensorboard library on Macos requires python version >= 3.9

[donggook-me]

Why are these changes needed?

< I am trying to run this framework on my local MacOs(M1 chip). but when I run mentioned(on readme) creating env command, error happens. because tensorboard library on Macos requires python version >= 3.9.

Related issue number

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Checks

• [ ] I've included any doc changes needed for https://fedscale.readthedocs.io/en/latest/
• [ ] I've made sure the following tests are passing.
• Testing Configurations
  • [ ] Dry Run (20 training rounds & 1 evaluation round)
  • [ ] Cifar 10 (20 training rounds & 1 evaluation round)
  • [ ] Femnist (20 training rounds & 1 evaluation round)

[fanlai0990]

It looks good to me. Thanks for your contribution.