This commit just removes some unnecessary using declarations

Change-Id: Ia1c7cc925b2db5b1172fae91dc703883d6539eaa
Signed-off-by: José Guilherme Vanz <guilherme.sft@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/1430Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>