From Google's Developer website:
The Google Play Services for AR service is installed automatically, either during app install, or at runtime when beginning an ARCore session.
One of the apps you're using wants to use AR. Unfortunately, this automatic installation is a side effect of Google Play being used to being a system app that can do whatever it wants, so on GrapheneOS it just sits there, confused and pending. Play will continue to attempt to install it.
You have two ways to stop this from happening: install it and remove its permissions, or install it then disable it at Settings > Apps > All Apps > Google Play Services for AR > Disable