Keyboard: fix redundant leave/enter on creation

Currently if a second keyboard input device is created river will send
a wl_keyboard.leave event immediately followed by a wl_keyboard.enter
event. This serves no purpose and can confuse clients, in particular due
to fctix creating/destroying virtual keyboards on focus change.

Fixes: https://codeberg.org/river/river/issues/1062
References: fcitx/fcitx5#1044

river/Seat.zig

@@ -489,7 +489,6 @@ fn tryAddDevice(seat: *Seat, wlr_device: *wlr.InputDevice) !void {
 
             seat.wlr_seat.setKeyboard(keyboard.device.wlr_device.toKeyboard());
             if (seat.wlr_seat.keyboard_state.focused_surface) |wlr_surface| {
-                seat.wlr_seat.keyboardNotifyClearFocus();
                 seat.keyboardNotifyEnter(wlr_surface);
             }
         },