mac build: set minimum system version to 10.13.0 in Info.plist
mac build: set minimum system version to 10.13.0 in Info.plist

based on https://github.com/Electron-Cash/Electron-Cash/commit/907e5e7009e00815f8df3925c50e8d246d3d0359

This way users get more feedback from the OS when they attempt to launch the app on old macOS.

Co-authored-by: Calin Culianu <57549f2037ccc250f2203dbfbed8f6f454d58f12@gmail.com>

pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum,pooler/electrum-ltc,pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum,pooler/electrum-ltc