How to stop MS AutoUpdate prompt
The message is provided by Microsoft AutoUpdate.
You can disable the message without removing AU by setting the following key:

defaults write com.microsoft.autoupdate2.plist \
    AcknowledgedDataCollectionPolicy RequiredDataOnly


https://derflounder.wordpress.com/2019/07/23/suppressing-microsoft-autoupdates-required-data-notice-screen/

To completely remove AU from your system, delete the following:


/Library/Application Support/Microsoft/MAU2.0/
~/Library/Application Support/Microsoft AutoUpdate/
~/Library/Preferences/com.microsoft.autoupdate2.plist
~/Library/Preferences/com.microsoft.autoupdate.fba.plist
/Library/LaunchAgents/com.microsoft.update.agent.plist