doc: Use Screen and OpenSSH in the bare-bones example.

* gnu/system/examples/bare-bones.tmpl (packages): Remove TCPDUMP; add
SCREEN and OPENSSH.
* doc/guix.texi (Using the Configuration System): Adjust explanation
accordingly.

doc/guix.texi

@@ -8186,8 +8186,9 @@ environment variable---in addition to the per-user profiles
 provides all the tools one would expect for basic user and administrator
 tasks---including the GNU Core Utilities, the GNU Networking Utilities,
 the GNU Zile lightweight text editor, @command{find}, @command{grep},
-etc.  The example above adds tcpdump to those, taken from the @code{(gnu
-packages admin)} module (@pxref{Package Modules}).  The
+etc.  The example above adds GNU@tie{}Screen and OpenSSH to those,
+taken from the @code{(gnu packages screen)} and @code{(gnu packages ssh)}
+modules (@pxref{Package Modules}).  The
 @code{(list package output)} syntax can be used to add a specific output
 of a package:
 

gnu/system/examples/bare-bones.tmpl

@@ -3,7 +3,7 @@
 
 (use-modules (gnu))
 (use-service-modules networking ssh)
-(use-package-modules admin)
+(use-package-modules screen ssh)
 
 (operating-system
   (host-name "komputilo")
@@ -40,7 +40,7 @@
                %base-user-accounts))
 
   ;; Globally-installed packages.
-  (packages (cons tcpdump %base-packages))
+  (packages (cons* screen openssh %base-packages))
 
   ;; Add services to the baseline: a DHCP client and
   ;; an SSH server.