Bug 27673: Fix encoding issues - Dump

Bug 27673: Fix encoding issues - Dump

Same as Load, but for Dump.

Test plan:
Edit ES mappings, replace withdrawn's label with "withdrawn ✔️ ❤️ ★"
Export the mappings
  perl misc/search_tools/export_elasticsearch_mappings.pl > admin/searchengine/elasticsearch/mappings.yaml
Reset mappings from the UI
=> Notice that the label is correct

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@helsinki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>