MAINT: bump to Python 3.10

[GaelVaroquaux]

Currently, we only want as users people who are early adopters and quite agile.

I'm in favor of dropping support for Python versions earlier than 3.10. If nothing else, it will make our build matrix lighter.

[GaelVaroquaux]

To be merged after #605 is merged

[glemaitre]

Uhm I might not have the rights :) but I wanted to rename "dump" to "bump" in the title of the PR :)

[GaelVaroquaux]

Did I get things wrong: I see that the tests still run Python 3.9 and 3.8?

Is it because the build matrix of a PR is changed only with the yml is changed in the main branch?

[LilianBoulard]

Is it because the build matrix of a PR is changed only with the yml is changed in the main branch?

I don't think so, but maybe 🤔
Your changes seem alright though, so I'd up for merging, fix later if necessary

[Vincent-Maladiere]

I can't comment on it, but you want to remove "3.8" and "3.9" in L34 from test.yml

python-version: ["3.8", "3.9", "3.10"]

[GaelVaroquaux]

I can't comment on it, but you want to remove "3.8" and "3.9" in L34 from test.yml

Good eye!!

[LilianBoulard]

Amazing! Merging :)

[Vincent-Maladiere]

There's an issue with the CI strategy matrix, it should be:

            include:
              - os: "ubuntu-latest"
                os-name: "Ubuntu"
              - os: "macos-latest"
                os-name: "MacOS"
              - dependencies-version: "dev"
              - dependencies-version: "dev, min-py310"
                python-version: "3.10"
                dependencies-version-type: "minimal"   

I created a revert by mistake; I'm creating another PR to fix it.