fix: remove the warning because it's wrong

/run/credentials is stable for system services.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

nix/modules/vault-secrets.nix

@@ -20,8 +20,6 @@ let
           defaultText = "/run/credentials/$service.service/$name";
           description = ''
             Absolute path to systemd's loaded credentials.
-            WARNING: Using this path might break if systemd in future decides to use
-            a different location but /run/credentials
           '';
         };
       };