A few days after it was released, I installed the first beta of OS X 10.11 El Capitan on my MacBook Air (Early 2015 model). The El Capitan beta has been running more or less stable and I only had some minor issues that were resolved in later beta releases.
It hasn't occurred to me to check my OS X version for a while. Upon doing so now, OS X still reads "OS X 10.11 Beta", but the Mac App Store doesn't display an available update.
How can I update to the latest retail version of OS X El Capitan?