doc: yama: Swap HTTP for HTTPS and replace dead link

doc: yama: Swap HTTP for HTTPS and replace dead link

Replace one dead link for the same person's original presentation on the
topic and swap an HTTP URL with HTTPS. While here, linkify the text to
make it more readable when rendered.

Link: https://lore.kernel.org/lkml/20200708073346.13177-1-grandmaster@al2klimov.de/
Co-developed-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/202007091141.C008B89EC@keescook
Signed-off-by: Jonathan Corbet <corbet@lwn.net>