Code Review: LGTM

This is a clean, minimal change. The geneSynonyms field was already defined in the ES mapping (Mapping.java:96), search helper (SearchHelper.java:186), indexer cache (IndexerCache.java:33,101), and searchable item document (SearchableItemDocument.java:78). This PR fills in the missing piece by:

1. Adding the geneSynonyms field (Set<String>) to AlleleSearchResultDocument — type matches the existing field in SearchableItemDocument.
2. Populating it in AlleleSearchResultConverter from AlleleSummaryDocument, following the same null/empty guard pattern used by all surrounding fields.
3. Bumping the curation dependency to v0.47.31 (which presumably adds getGeneSynonyms() to AlleleSummaryDocument).

No issues found.