Don't sanitize IME composition input on the SDL2TextInput side
Don't sanitize IME composition input on the SDL2TextInput side

By sanitizing in TextBox only, we can call `NotifyInputError()` to let the user know.

ppy/osu-framework,ppy/osu-framework,smoogipooo/osu-framework,peppy/osu-framework,peppy/osu-framework,smoogipooo/osu-framework,peppy/osu-framework,ppy/osu-framework