mattermost: cosmetic: remove stray character (#17897)

Changed files
+1 -1
nixos
modules
services
web-apps
+1 -1
nixos/modules/services/web-apps/mattermost.nix
···
type = types.str;
example = "https://chat.example.com";
description = ''
-
URL this Mattermost instance is reachable under, without trailing slash."
+
URL this Mattermost instance is reachable under, without trailing slash.
'';
};