fix: Increase the default delay before showing long-press diacritics

Since 6.7 there have been more people using the feature, and several complaining that it pops up when they are just typing.

Lets assume that most people are much more slow and hesitant at typing than us techies, and increase the default delay to 600ms; the same that the key repeat delay is set to by default.

I played around with a few values, trying to pretend I type slowly and hesitantly, and that one seemed relatively safe.

This should fix the accidental overlays for most people, and anyone who uses it regularly can still easily change the setting to a lower value if they prefer.