Update PEP 11: bump Windows on Arm to Tier 2

Hello,

we want to update the PEP 11 by bumping Windows on Arm to Tier-2. This is the result of the discussion we held on here https://discuss.python.org/t/python-on-windows-arm64/104524/ and a few discussions at EuroPython.

Related PR: https://github.com/python/peps/pull/5046