This commit removes some ::rtl:: prefixes on oox

Change-Id: Ibb3be70695c48eb0a02fdf285a0c049e244d613e
Signed-off-by: José Guilherme Vanz <guilherme.sft@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/1259Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>