go.tools/go/types: fix typo in self test
go.tools/go/types: fix typo in self test

R=adonovan
CC=golang-dev
https://golang.org/cl/11749044

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