ci: test: update tested Python versions

Drop 3.6 (EOL) and add 3.9/3.10.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>
GitOrigin-RevId: 5d37e1514ce18960c6fbec19a576b81c746b092c
Change-Id: I237f5063d257576a5ee186aa6a71e1b337c07ba3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/hal_stm32/+/3537949
Tested-by: CopyBot Service Account <copybot.service@gmail.com>
Reviewed-by: Yuval Peress <peress@google.com>
Commit-Queue: Yuval Peress <peress@google.com>
Tested-by: Yuval Peress <peress@google.com>