Ignore opening web tabs when opening newtab notifications

Background

Notifications of the type "newtab" are causing a new tab to be opened after the user opens a new tab. Some of those new tabs may be the result of an ongoing navigation (e.g. opening a link in a new tab) and therefore may be distracting and cause confusion.

See https://gitlab.com/eyeo/adblockplus/abpui/adblockplusui/-/issues/831

What to change

• Don't open newtab notifications yet when the user opens a new tab that's loading a web page.