Do not make numbers translatable in Help contents

Spare time and energy of translators by marking numbers non-translatable.

Change-Id: I99846db2271e27761ecf5498ce1456b3adcd84dc
Reviewed-on: https://gerrit.libreoffice.org/12493
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>