restoretab.js was added in https://github.com/mozilla/pdf.js/pull/6233
with the purpose of restoring lost tabs when Chrome closes all extension
tabs when it reloads the extension. This forced reload can happen when
the user toggles the "Allow access to file URLs" option.
This logic does not work any more, and since the use of localStorage is
a blocker in migrating to MV3, this patch just drops the logic.
bc4890d4d4
