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

Change-Id: Iae9a89f8a869934b6273a1b97c0a9243b0504fb3
Signed-off-by: José Guilherme Vanz <guilherme.sft@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/1260Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>