[release-branch.go1.13] doc/go1.13: add missing slashes
This saves a redirect and makes the document more consistent.
Change-Id: Ib7f68b1967275c0c676a044314919449680297f3
Reviewed-on: https://go-review.googlesource.com/c/go/+/191537
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
(cherry picked from commit
89fb80f7fae1359a57968fbe600fc69b7296dd2d)
Reviewed-on: https://go-review.googlesource.com/c/go/+/191740
Reviewed-by: Toshihiro Shiino <shiino.toshihiro@gmail.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>