You need to rebuild qt5-webkit first.
QuiteRSS depends on qt5-webkit which depends on icu.
pamac build qt5-webkit
then rebuild quiterss and any other package that depends on qt5-webkit
To see all packages that depend on qt5-webkit:
pactree -r qt5-webkit
If you do not want to rebuild qt5-webkit you could install icu73-bin from the AUR, which is a workaround, then you will not need to rebuild qt5-webkit or quiterss… but it will probably produce warning messages every time you use pamac/pacman, theses messages can be ignored but can be annyoing. 