Specify IP subnet literals in canonical form (#16953)

This is needed, because the netaddr package removed support for the
implicit prefix form in version 1.0.0:
netaddr/netaddr#360

Author: V02460

changelog.d/16953.misc

@@ -0,0 +1 @@
+Specify IP subnets in canonical form.

tests/api/test_auth.py

@@ -128,7 +128,7 @@ def test_get_user_by_req_appservice_valid_token_good_ip(self) -> None:
             token="foobar",
             url="a_url",
             sender=self.test_user,
-            ip_range_whitelist=IPSet(["192.168/16"]),
+            ip_range_whitelist=IPSet(["192.168.0.0/16"]),
         )
         self.store.get_app_service_by_token = Mock(return_value=app_service)
         self.store.get_user_by_access_token = AsyncMock(return_value=None)
@@ -147,7 +147,7 @@ def test_get_user_by_req_appservice_valid_token_bad_ip(self) -> None:
             token="foobar",
             url="a_url",
             sender=self.test_user,
-            ip_range_whitelist=IPSet(["192.168/16"]),
+            ip_range_whitelist=IPSet(["192.168.0.0/16"]),
         )
         self.store.get_app_service_by_token = Mock(return_value=app_service)
         self.store.get_user_by_access_token = AsyncMock(return_value=None)