go/types: reenable disabled test (backport from std repo go/types)
go/types: reenable disabled test (backport from std repo go/types)

Change-Id: I93a914dcfc5bd2cfa8078cec683a46225b665e44
Reviewed-on: https://go-review.googlesource.com/8626
Reviewed-by: Alan Donovan <7069e9552f9d110b0a0f326b96f22f63fb99dfc1@google.com>

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