update(mPropertyBag) {
			return _validateAndAdjustPropertyBag(mPropertyBag)
			.then(_checkSettingsAndExecuteActionByName.bind(this, "updateAppVariant"));
		}
Updates the app variants in the back end.

@param {object} mPropertyBag - Object with parameters as properties
@param {string} mPropertyBag.appId - App variant ID

@param {string} [mPropertyBag.transport] - Transport request for the app variant;
Transport is required for onPremise systems until the app variant is not intended to be updated as a local object;
Transport is not required for S4/Hana Cloud systems

@returns {Promise} Promise which gets resolved with the app variant update response or gets rejected with a first error
@private
@ui5-restricted