A knowledge base article about Repeated "GoogleUpdater" background Notifications on Macs provided by the UC Berkeley IT Service Hub - Knowledge Portal
Every time Google updates their "GoogleUpdater" utility program it triggers macOS to treat the update as a new installation, resulting in a macOS notification intended to keep users informed.
The behavior is caused by Google software programming interacting with Apple's "Transparency and Privacy" features. There is no way to suppress these system level notifications other than to entirely disable Google updates, which would then leave users without current versions of Google Chrome and Google Drive.
In macOS Tahoe the text will read:
"App Background Activity"
In earlier versions of macOS the text will read:
"Background Items Added"
Log for updates pushed from Google to the Mac can be read in:
/Library/Application Support/Google/updater.log
The currently installed version of GoogleUpdater.app will be:
/Library/Application Support/Google/GoogleUpdater/Current/GoogleUpdater.app