Remove a stray assignment dating from February 2012

The integer \l_tl_build_offset_int was removed from
l3tl-build a long time ago, but since we did not have
tests for Unicode-aware engines at the time, I forgot
to remove an assignment there.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5027 de43f980-851b-0410-b2f7-c40aca1f87e0
Comment on a possible improvement of l3str-convert


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5028 de43f980-851b-0410-b2f7-c40aca1f87e0