Fix wayland keyrepeat: use modifier-independant keycode instead of keysym

[jakobhellermann]

fix bug introduced by #11052

https://github.com/zed-industries/zed/pull/11052#issuecomment-2080475491 the keysym for a pressed with or without shift is different, so keyrepeat was never ended for Shift-A.

Release Notes:

• N/A