The version of Chrome in App Center is not packaged by Google but by the developers of Endless OS, which is currently at version 104. The current version of Chrome as published by Google is at 108, so there’s a slight version delay here. Recent versions of Chrome check if they are slightly out of date and nag the user to upgrade - which is not possible on Endless OS as it relies on the version from App Center.
So simply wait until a new version arrives in App Center and ignore the update nag for now.