tests: cleanup test code

- remove unused imports in test cases
- fix code smells and code style in conftest.py

test/test_acme_http_challenge_location/test_acme_challenge_location_disabled.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_redirect_acme_challenge_location_disabled(docker_compose, nginxproxy, acme_challenge_path):
     r = nginxproxy.get(
         f"http://web1.nginx-proxy.tld/{acme_challenge_path}",

test/test_acme_http_challenge_location/test_acme_challenge_location_enabled_is_default.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_redirect_acme_challenge_location_enabled(docker_compose, nginxproxy, acme_challenge_path):
     r = nginxproxy.get(
         f"http://web1.nginx-proxy.tld/{acme_challenge_path}",

test/test_acme_http_challenge_location/test_acme_challenge_location_legacy.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_redirect_acme_challenge_location_legacy(docker_compose, nginxproxy, acme_challenge_path):
     r = nginxproxy.get(
         f"http://web1.nginx-proxy.tld/{acme_challenge_path}",