Updates notification shown for users who have opted-out of notifications

Environment

• OS version: Ubuntu 16.04
• Browser version: Chrome 80
• Extension version: UI release 2019-3
• Last working version: N/A

Steps to reproduce

1. Update extension or increment updatesVersion in lib/prefs.js and reload extension.
2. Uncheck "Show useful notifications" in Advanced tab in desktop settings page.
3. Increment updatesVersion and reload extension again.

Observed behavior

• After 1) Updates notification shown.
• After 3) Updates notification shown.

Expected behavior

• After 1) Updates notification shown.
• After 3) Updates notification not shown.

Further information

See discussion.

Integration notes

Requires https://gitlab.com/eyeo/adblockplus/adblockpluscore/-/issues/196