Remove saved list from back-end

[SupeDeDupe]

There are fragments of code that may be reused when the favourites' replacement feature is implemented. Once the new feature is implemented, all pieces of the saved list should be removed. This includes the

• icon files;
• the commented out sections from in sticky_header, sticky_header_test, and benefit_card;
• the favouriteBenefits variable in store.js and all of the places it is referenced as state.favouriteBenefits;
• favouritesUrl;
• the favourites page;
• the favourites component;
• the favourites_button component;
• the disabled cookies banner;