ci: remove xfail from tests that were fixed

test/stress_tests/test_deleted_cert/test_restart_while_missing_cert.py

@@ -9,8 +9,6 @@ from requests import ConnectionError
 
 script_dir = os.path.dirname(__file__)
 
-pytestmark = pytest.mark.xfail()  # TODO delete this marker once those issues are fixed
-
 
 @pytest.fixture(scope="module", autouse=True)
 def certs():

test/stress_tests/test_unreachable_network/test_unreachable_net.py

@@ -3,8 +3,6 @@ from time import sleep
 import pytest
 import requests
 
-pytestmark = pytest.mark.xfail()  # TODO delete this marker once #585 is merged
-
 
 def test_default_nginx_welcome_page_should_not_be_served(docker_compose, nginxproxy):
     r = nginxproxy.get("http://whatever.nginx-proxy/", allow_redirects=False)