[3.11] gh-105821: Use a raw f-string in test_httpservers.py (GH-105822) (#108576)

gh-105821: Use a raw f-string in test_httpservers.py (GH-105822)

Use a raw f-string in test_httpservers.py
(cherry picked from commit 09ce8c3b48f940eb8865330f029b8069854c3106)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>