EstablishmentMeans should be a string vocabulary, not a JSON object based on the latest DWC

[qifeng-bai]

Originally reported by @nielsklazenga

https://biocache-ws-databox.ala.org.au/ws/occurrences/3afe9be0-f4fd-41d7-b6df-2a5117e08757
Valued of processed->occurrence->establishmentMeans is an json: 'establishmentMeans: "{"concept": "vagrant", "lineage": ["vagrant"]}"'

Our current EstablishmentMean model has two fields: concept and lineage, but EstablishmentMean in the latest DWC core is defined as a controlled value string
refer: https://dwc.tdwg.org/em/

It has the same issue on our Biocache prod

Todo:
Fix on building indexRecord stage to avoiding changing BasicRecord model:

https://github.com/gbif/pipelines/blob/dev_ala_events/livingatlas/pipelines/src/main/java/au/org/ala/pipelines/transforms/IndexRecordTransform.java#L130

Link to: AtlasOfLivingAustralia/la-pipelines#525