go.tools/godoc/redirect: remove race detector blog post redirect
go.tools/godoc/redirect: remove race detector blog post redirect

Update issue 7275

LGTM=minux.ma, dvyukov
R=dvyukov, minux.ma
CC=golang-codereviews
https://codereview.appspot.com/60900044

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