system: Remove unused yggdrasil OS template.

This file was added in fe1cd098d2 but it's
not referenced from anywhere, not even gnu/local.mk.  Furthermore, we
don't normally add full OS examples for the purposes of illustrating the
use of a single service.

* gnu/system/examples/yggdrasil.tmpl: Remove.

gnu/system/examples/yggdrasil.tmpl

@@ -1,60 +0,0 @@
-;; This is an operating system configuration template
-;; for a "bare bones" setup, with no X11 display server.
-
-(use-modules (gnu))
-(use-service-modules networking ssh)
-(use-package-modules admin curl networking screen)
-
-(operating-system
-  (host-name "ruby-guard-5545")
-  (timezone "Europe/Budapest")
-  (locale "en_US.utf8")
-
-  ;; Boot in "legacy" BIOS mode, assuming /dev/sdX is the
-  ;; target hard disk, and "my-root" is the label of the target
-  ;; root file system.
-  (bootloader (bootloader-configuration
-                (bootloader grub-bootloader)
-                (targets '("/dev/sdX"))))
-  (file-systems (cons (file-system
-                        (device (file-system-label "my-root"))
-                        (mount-point "/")
-                        (type "ext4"))
-                      %base-file-systems))
-  (users (cons (user-account
-                (name "alice")
-                (comment "Bob's sister")
-                (group "users")
-                ;; adding her to the yggdrasil group means she can use
-                ;; yggdrasilctl to modify the configuration
-                (supplementary-groups '("wheel" "yggdrasil")))
-               %base-user-accounts))
-
-  ;; Globally-installed packages.
-  (packages (cons* screen curl %base-packages))
-
-  ;; Add services to the baseline: a DHCP client and
-  ;; an SSH server.
-  ;; If you add an /etc/yggdrasil-private.conf, you can log in to ssh
-  ;; using your Yggdrasil IPv6 address from another machine running Yggdrasil.
-  ;; Alternatively, the client can sit behind a router that has Yggdrasil.
-  ;; That file is specifically _not_ handled by Guix, because we don't want its
-  ;; contents to sit in the world-readable /gnu/store.
-  (services
-   (append
-    (list
-     (service dhcp-client-service-type)
-     (service yggdrasil-service-type
-              (yggdrasil-configuration
-               (log-to 'stdout)
-               (log-level 'debug)
-               (autoconf? #f)
-               (json-config
-                ;; choose a few from
-                ;; https://github.com/yggdrasil-network/public-peers
-                '((peers . #("tcp://1.2.3.4:1337"))))
-               (config-file #f)))
-     (service openssh-service-type
-              (openssh-configuration
-               (port-number 2222))))
-    %base-services)))