DEPS: remove duplicated dependency in requirement-dev.txt
I think this is already tested here essentially? https://github.com/pandas-dev/pandas/blob/705d4312cf1d94ef2497bcd8091e0eabd1085f4a/.github/workflows/code-checks.yml#L156 > I think this is already tested here essentially?
> 
> https://github.com/pandas-dev/pandas/blob/705d4312cf1d94ef2497bcd8091e0eabd1085f4a/.github/workflows/code-checks.yml#L156

Seems so. Then I wondered why it didn't catch the double requirements given error. I'll remove the CI check and make this PR a simple fix. Thanks @fangchenli 