how do you update the wireless controller on mac?

The only way to update the wireless controller in the Mac is to keep the software updated or by upgrading the macOS software.

Device drivers and firmware updates are built into macOS software updates and upgrades and are not generally available individually. From time to time Apple will address a critical problem by issuing a specific update for software or firmware.

If your Xbox Controller needs a firmware update you probably need access to a Windows PC.

https://support.xbox.com/en-US/help/hardware-network/controller/update-xbox-wireless-controller