input-device: drop wlr_input_device.{vendor,product}

These aren't super useful without the bus type. Compositors can
fish back this information from the libinput device if they want to.

Closes: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3818

include/wlr/types/wlr_input_device.h

@@ -36,12 +36,9 @@ enum wlr_input_device_type {
  *
  * Input devices are typically advertised by the new_input event in
  * struct wlr_backend.
- *
- * The vendor/product are bus-specific identifiers.
  */
 struct wlr_input_device {
 	enum wlr_input_device_type type;
-	unsigned int vendor, product;
 	char *name; // may be NULL
 
 	struct {