Mixpanel Integration Group Properties can't be overwritten due to .set_once() call

[rpatel05]

analytics.js-integrations/integrations/mixpanel/lib/index.js

Lines 339 to 345 in 1f21d51

	if (traits && Object.keys(traits).length) {
	for (var ind = 0; ind < groupIdentifierTraits.length; ind++) {
	window.mixpanel
	.get_group(groupIdentifierTraits[ind], groupId)
	.set_once(traits);
	}
	}

Mixpanel integration Group properties call is passed in as set_once(traits) making it so that group props can never be overwritten if the value changes. Suggest changing it to a .set(traits) call or I know a Segment team member considered adding a toggle such as:

if (useSetInGroupCalls === true) {
        window.mixpanel
        .get_group(groupIdentifierTraits[ind], groupId)
        .set(traits);
} else {
      window.mixpanel
        .get_group(groupIdentifierTraits[ind], groupId)
        .set_once(traits);
}