install: Show the "System Installation" node.

* gnu/system/install.scm (log-to-info): Go to the new 'System
  Installation' node.

gnu/system/install.scm

@@ -40,7 +40,7 @@ (define (log-to-info)
                 #~(execl (string-append #$texinfo-4 "/bin/info") "info"
                          "-d" "/run/current-system/profile/share/info"
                          "-f" (string-append #$guix "/share/info/guix.info")
-                         "-n" "System Configuration")))
+                         "-n" "System Installation")))
 
 (define (installation-services)
   "Return the list services for the installation image."