You can turn them off, but individually per app.
go to the Secure Folder settings (Settings app, Biometrics and Security, Secure Folder).
Tap "Notifications and data"
Tap "App notifications"
Tap "More"
Tap where it days "Most Recent" then select "All" from the list I've screenshotted.
Then scroll down to find Google Play - there were 3 apps for me. Turn them all off.