go.tools/cmd/godoc: use playground package from go.tools
go.tools/cmd/godoc: use playground package from go.tools

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/11507044

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