An either without an or doesn't add anything.
* @seat: the object on which the signal is emitted
* @device: the newly added #GdkDevice.
*
- * The ::device-added signal is emitted either when a new input
+ * The ::device-added signal is emitted when a new input
* device is related to this seat.
*
* Since: 3.20
* @seat: the object on which the signal is emitted
* @device: the just removed #GdkDevice.
*
- * The ::device-removed signal is emitted either when an
+ * The ::device-removed signal is emitted when an
* input device is removed (e.g. unplugged).
*
* Since: 3.20