go.tools/cmd/godoc: remove useless code from index.go
go.tools/cmd/godoc: remove useless code from index.go

This code was moved to a throttle method on Corpus but I guess it was
never deleted.

LGTM=crawshaw
R=golang-codereviews, crawshaw
CC=golang-codereviews
https://golang.org/cl/102350043

maddyonline/tools,syreclabs/go-tools,jdhenke/tools,matryer/tools,josharian/tools,jdhenke/tools,springning/tools,dmitris/tools,maddyonline/tools,magiccao/tools,syreclabs/go-tools,runcom/tools,argandas/tools,magiccao/tools,syreclabs/go-tools,springning/tools,glasser/golang-tools,golang/tools,josharian/tools,syreclabs/go-tools,matryer/tools,runcom/tools,sshetty10/tools,maddyonline/tools,cw2018/tools,cmars/tools,syreclabs/go-tools,argandas/tools,matryer/tools,magiccao/tools,syreclabs/go-tools,maddyonline/tools,glasser/golang-tools,nicot/tools,golang/tools,josharian/tools,golang/tools,dmitris/tools,4ad/tools,dmitris/tools,nicot/tools,cw2018/tools,cw2018/tools,josharian/tools,golang/tools,springning/tools,argandas/tools,runcom/tools,sshetty10/tools,glasser/golang-tools,matryer/tools,nicot/tools,sshetty10/tools,nicot/tools,4ad/tools,glasser/golang-tools,cmars/tools,sshetty10/tools,jdhenke/tools,magiccao/tools,cmars/tools,cmars/tools,4ad/tools,cw2018/tools,jdhenke/tools,springning/tools,argandas/tools,golang/tools,runcom/tools,dmitris/tools