gddo-server/assets/templates: use HTTPS for links
gddo-server/assets/templates: use HTTPS for links

Fixes golang/gddo#496.

Change-Id: I48a7ea476fb40037d32c136e03227b455dee5f10
Reviewed-on: https://go-review.googlesource.com/49651
Reviewed-by: Dmitri Shuralyov <0c2a7749d909c8353e59c3f9c6a4d19a5ce000c1@gmail.com>

segmentio/gddo,segmentio/gddo,golang/gddo,golang/gddo,golang/gddo,golang/gddo,segmentio/gddo,segmentio/gddo