nixos/coturn: fix documentation link formatting

Changed files
+1 -1
nixos
modules
services
networking
+1 -1
nixos/modules/services/networking/coturn.nix
···
This feature can be used with the long-term authentication mechanism, only.
This feature purpose is to support "TURN Server REST API", see
"TURN REST API" link in the project's page
-
https://github.com/coturn/coturn/
This option is used with timestamp:
···
This feature can be used with the long-term authentication mechanism, only.
This feature purpose is to support "TURN Server REST API", see
"TURN REST API" link in the project's page
+
<https://github.com/coturn/coturn/>
This option is used with timestamp: