remove leftover legacy picviewer.lua
remove leftover legacy picviewer.lua

NiLuJe/koreader,NiLuJe/koreader,NickSavage/koreader,mwoz123/koreader,poire-z/koreader,Markismus/koreader,koreader/koreader,Frenzie/koreader,robert00s/koreader,poire-z/koreader,mihailim/koreader,pazos/koreader,frankyifei/koreader,noname007/koreader,koreader/koreader,chihyang/koreader,ashang/koreader,Frenzie/koreader,lgeek/koreader,chrox/koreader,houqp/koreader,Hzj-jie/koreader,ashhher3/koreader,apletnev/koreader