Fix manual error

Reported by Matija Šuklje.

Fixes #163.

doc/manual/package-management.xml

@@ -225,7 +225,7 @@ uses is to create directory trees of symlinks to
 themselves (though automatically generated by
 <command>nix-env</command>), so they too reside in the Nix store.  For
 instance, in <xref linkend='fig-user-environments' /> the user
-environment <filename>/nix/store/5mq2jcn36ldl...-user-env</filename>
+environment <filename>/nix/store/0c1p5z4kda11...-user-env</filename>
 contains a symlink to just Subversion 1.1.2 (arrows in the figure
 indicate symlinks).  This would be what we would obtain if we had done