SDL3: `TrackedSetting` for `WindowedSize` is no longer updated during a resize on windows

[Susko3]

• Regressed with ff2ee9d

Noticed while looking into https://discord.com/channels/188630481301012481/589331078574112768/1326546222839889941.

This regresses the osu!-side screen resolution popup, it'll only show once the resize is finished:

[peppy]

I'd see this as pretty important to fix, because without it it makes getting the window size to a specific dimension that the user wants quite hard.