chore: Python 3.12 is the floor (NAPALM/driver-standard#6)

netOrk runs every driver in its own containers on Python 3.12, so 3.10
and 3.11 are no longer supported or tested. requires-python, mypy and
ruff move to 3.12, along with what ruff's pyupgrade rules then rewrite.

README.md

@@ -390,7 +390,7 @@ detection vs. presentation there.
 pip install napalm-device-types
 ```
 
-Requires Python ≥ 3.10 (tested up to 3.13) and NAPALM ≥ 4.0.
+Requires Python ≥ 3.12 (tested up to 3.13) and NAPALM ≥ 4.0.
 
 ## Available base classes