word [skip ci]

[http header] setting --> [http header] header

src/default_settings.py

@@ -42,7 +42,7 @@
 PythonAnywhere, but with Nginx, you should add this line to your server block:
         proxy_set_header        X-Forwarded-For  $proxy_add_x_forwarded_for;
 Apache/other proxies should also set the header to the real user IP.
-If you enable this option, you MUST set the X-Forwarded-For setting.
+If you enable this option, you MUST set the X-Forwarded-For header.
 """
 USE_X_FORWARDED_FOR = False