CI: Mambaforge upgrade base image to 3.10 in docker build

[phofl]

Mambaforge upgraded the python version to 3.10 in their image causing our builds to fail. The first affected version is 4.14.0-0

Failing build:
https://github.com/pandas-dev/pandas/runs/8171619523?check_suite_focus=true

[mroeschke]

Generally, it's probably not great that in our Dockerfile that we're trying to update the base 3.10 environment with our 3.8 environment.yml as it appears conda/mamba is still trying to use 3.10 packages to update the environment.

A guess also is that downgrading certifi here (because of installing environment.yml?) is also probably not good.

  - certifi                                2022.6.15  py310hff52083_0     conda-forge                   
  + certifi                                2022.6.15  pyhd8ed1ab_1        conda-forge/noarch       158kB

[phofl]

No this isn’t great. We should bump our python version at some point