Fix language code concatenation orginating from the <oai_dc> in the public XML

[andrewjbtw]

The <oai_dc> element in the public XML is used to generate IIIF manifests, which then power the metadata display in Mirador and (soon) the Media viewer.

There is a problem somewhere in the transformation into <oai_dc> that's causing language codes to be concatenated:

<dc:language>ArabicaraArabicArab</dc:language>

This string is then ending up in embed viewers:

There's a stylesheet that generated DC from MODS that is probably the source of the issue:
https://github.com/sul-dlss/dor-services-app/blob/main/app/services/publish/mods2dc.xslt

[andrewjbtw]

It occurs to me now that I understand where the DC is created, this ticket should move to the DSA repo. I'll see if I can do that myself.