update doc for `instanceName` for macOS
update doc for `instanceName` for macOS

Co-authored-by: Jared McFarland <420d97235124da5bf24c51a35edb1119f653ce09@mixpanel.com>
mixpanel/mixpanel-swift,mixpanel/mixpanel-swift,mixpanel/mixpanel-swift,mixpanel/mixpanel-swift,mixpanel/mixpanel-swift