Upgrade mac-drive-2 to 10.13.6 (High Sierra)

In order to be ble to ship notarized applications on macOS, the app needs to be built on macOS 10.13. So install that version on 1 agent only (for now).

As required by NXDRIVE-2041, MAC-DRIVE-2 must be upgraded from macOS 10.12.6 (Sierra) to 10.13.6 (High Sierra).

According to https://support.apple.com/en-us/HT208969, High Sierra can be downloaded from https://itunes.apple.com/us/app/macos-high-sierra/id1246284741?ls=1&mt=12.