java: unused imports

Change-Id: I05824a6f19a5f3048a52101b96f6bf3d3099df08
Reviewed-on: https://gerrit.libreoffice.org/13403
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>