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/http/test_proxy.py

@@ -18,7 +18,6 @@
 # [This file includes modifications made by New Vector Limited]
 #
 #
-from typing import Set
 
 from parameterized import parameterized
 
@@ -64,7 +63,7 @@ class ProxyTests(TestCase):
     def test_parse_connection_header_value(
         self,
         connection_header_value: bytes,
-        expected_extra_headers_to_remove: Set[str],
+        expected_extra_headers_to_remove: set[str],
     ) -> None:
         """
         Tests that the connection header value is parsed correctly