Use Python 3.10 in Cirrus CI for typecheck

[abravalheri]

For some reason the typechecker is failing in the GitHub action for Python 3.10, but not in the Cirrus CI.

Specifically the error is:

src/validate_pyproject/api.py:42: error: Module "importlib.resources" has no
attribute "files"  [attr-defined]
            from importlib.resources import files
            ^
Found 1 error in 1 file (checked 24 source files)

The GHA environment is:
``
CPython (3.10.2)
mypy==0.931,
mypy-extensions==0.4.3,
packaging==21.3,
pyparsing==3.0.7,
tomli==2.0.1,
trove-classifiers==2022.2.16,
typing_extensions==4.1.1

The Cirrus CI environment is:

mypy==0.931,
mypy-extensions==0.4.3,
packaging==21.3,
pyparsing==3.0.7,
tomli==2.0.1,
trove-classifiers==2022.2.16,
typing_extensions==4.1.1,

Maybe the best solution here is to downgrade one of CirrusCI or GHA to use Python 3.9 to run the typechecker...