Fix a systemd library version

was r11532.

chapter06/systemd.xml

@@ -239,7 +239,7 @@ chmod 755 /lib/systemd/systemd-user-sessions</userinput></screen>
         telinit, timedatectl, 以及 udevadm</seg>
         <seg>libnss_myhostname.so.2, libnss_mymachines.so.2,
         libnss_resolve.so.2, libnss_systemd.so.2, 
-        libsystemd.so, libsystemd-shared-231.so,
+        libsystemd.so, libsystemd-shared-&systemd-version;.so,
         以及 libudev.so</seg>
         <seg>/etc/binfmt.d, /etc/init.d, /etc/kernel, /etc/modules-load.d,
         /etc/sysctl.d, /etc/systemd, /etc/tmpfiles.d, /etc/udev,