removes starmaths InsertCommand in favour of InsertCommandText

Change-Id: I5659adcaa28e5b5861d1a1cc5d2afa84009490f6
Reviewed-on: https://gerrit.libreoffice.org/37113Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>