Remove obsolete strings

[flodolo]

I was going through the strings, and I think there is a ton of obsolete content (haven't looked at the code, but I don't expect them to be referenced anywhere).

For example: there are still messages saying that Sync is not supported, or that multiple Notes will come soon, while they're already there.

That's an unnecessary hurdle for new localizations, they have no way to tell which strings are obsolete, and which are still relevant.

P.S. took the liberty of creating a Localization label