[fix] MenuSorter: use orderedPairs for orphans (#6403)
[fix] MenuSorter: use orderedPairs for orphans (#6403)

Skipped in <https://github.com/koreader/koreader/pull/6371>.
mwoz123/koreader,poire-z/koreader,koreader/koreader,NiLuJe/koreader,NiLuJe/koreader,Markismus/koreader,poire-z/koreader,koreader/koreader,Frenzie/koreader,Frenzie/koreader,pazos/koreader,Hzj-jie/koreader