content: add link to the Turkish translation

The translations page used to list the Turkish translation. But
the link is gone now, adding it again.

The Turkish Go Tour is a decent reference for Turkish terminology.
I haven't studied computer science in Turkish myself but don't
remember coming around a better modern document about programming
languages. I often recommend it as a terminology reference.

Change-Id: Ife11a245e25ec7964e9ae77365c8d07b1cc284db
Reviewed-on: https://go-review.googlesource.com/14406
Reviewed-by: Andrew Gerrand <adg@golang.org>
1 file changed