refactor: remove deprecated event keypress from TextField

[fourhundredfour]

Closes #121

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[Florian-Schoenherr]

Thank you!
The TextField.json is getting generated, so the description will vanish.
IMO, putting Deprecated - Use keyup or keydown instead behind the <input/> inside TextField.svelte is enough, due to keypress not being a prop.
Later we'll change it to use this: alexprey/sveltedoc-parser#30