Revert "updated" dates in l3prop: no behavior change

Since revision 4401 did not change the behavior of
any function, only the internal structure, the date
should not be changed to 2013-01-07.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4408 de43f980-851b-0410-b2f7-c40aca1f87e0