go.tools/ssa: remove workaround for missing go/types check, now fixed.
go.tools/ssa: remove workaround for missing go/types check, now fixed.

R=gri
CC=golang-dev
https://codereview.appspot.com/10921043

tmc/mirror-go.tools,tmc/mirror-go.tools,tmc/mirror-go.tools,t-yuki/go.tools.old,t-yuki/go.tools.old,t-yuki/go.tools.old