Use type hinting generics in standard collections (#19046)

aka PEP 585, added in Python 3.9

 - https://peps.python.org/pep-0585/
 - https://docs.astral.sh/ruff/rules/non-pep585-annotation/

tests/config/utils.py

@@ -24,7 +24,6 @@ import tempfile
 import unittest
 from contextlib import redirect_stdout
 from io import StringIO
-from typing import List
 
 from synapse.config.homeserver import HomeServerConfig
 
@@ -61,7 +60,7 @@ class ConfigFileTestCase(unittest.TestCase):
         with open(self.config_file, "w") as f:
             f.write("".join(contents))
 
-    def add_lines_to_config(self, lines: List[str]) -> None:
+    def add_lines_to_config(self, lines: list[str]) -> None:
         with open(self.config_file, "a") as f:
             for line in lines:
                 f.write(line + "\n")