Apple releases 2 2C54 firmware updates for the AirPods, although they are a lot less frequent than iOS updates. There are no new features are added but some minor improvements, such as performance with this C54 firmware for the AirPods 2 and AirPods Pro.
The update should be installed automatically in the background, however, there is a way to force the update, if the latest version is not yet installed. The best way to do this is to put the AirPods in the charging case, open the charging case, Then make sure the AirPods are connected to your iPhone and close the charging case. The update will now be installed. Keep in mind that it can take a while.
You can check for yourself whether the latest version is already installed on your AirPods by connecting the AirPods to your iPhone and in the Settings app go to General> Info> AirPods. You will see the current version number behind the firmware version.