Highlighting in toc still not accurate in all cases

[MoritzWeber0]

Go to https://www.fipguide.org/en/operator/sncf/#special-tariff-conditions. "Special Tariff Conditions" should be highlighted, but instead "Reservation requirement in regional trains" is highlighted. Maybe that's because of #370

[MoritzWeber0]

According to git bisect, it was introduced in #391 (16ccfdf#diff-215523d38d6c15f1b60a7afc252cc2841414757f34385b89900a7b13bb92d162). Not sure yet what it has changed or what it has to do with the toc.

EDIT: The position: relative in .o-container is responsible for it.