fixed doc template_directives

docs/api/configuration.md

@@ -242,7 +242,7 @@ ProxyConfig(listen_port=4242)   # Default
 ProxyConfig(listen_port=8080)   # Custom
 ```
 
-#### `template_vars: Optional[Dict[str, List[str]]]`
+#### `template_directives: Optional[Dict[str, List[str]]]`
 Additional variables to pass to template. Each key corresponds to the HAProxy template section where the directives must be added.
 
 **Default:** `{}`