pmb.config: Use Python 3.8-compatible type annotation

The 'list' type annotation only works from Python 3.9 and since we still
support Python 3.7 we should use the version from the typing package
instead.

Closes: https://gitlab.com/postmarketOS/pmbootstrap/-/issues/2247
Fixes: d31313f7 ("Don't use 'sudo' when running as root")
Reviewed-by: Oliver Smith <ollieparanoid@postmarketos.org>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230625193650.528651-1-luca@z3ntu.xyz%3E

pmb/config/__init__.py

@@ -4,6 +4,7 @@ import multiprocessing
 import os
 import pmb.parse.arch
 import sys
+from typing import List
 
 #
 # Exported functions
@@ -60,7 +61,7 @@ required_programs = [
 ]
 
 
-def sudo(cmd: list[str]) -> list[str]:
+def sudo(cmd: List[str]) -> List[str]:
     """Adapt a command to run as root."""
     sudo = which_sudo()
     if sudo: