Bug 31694: (follow-up) Use values for operations to avoid translation issues

Bug 31694: (follow-up) Use values for operations to avoid translation issues

    To test:
    * Try adding a preset rule that has an operation with different translations
      for the column and the pull down (e.g. Outrepasser for fr-CA)
    * Without the patch it appears as Custom (e.g. Personnalisé)
    * With the patch it appears correctly (e.g. Outrepasser)

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jan Kissig <jkissig@th-wildau.de>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>