fix: fix synonym delete response schema

[tharropoulos]

Change Summary

The current API spec defines the return schema of a successful DELETE request on the /collection/{collectionName}/synonyms/{synonymId} endpoint as SearchSynonym, matching the ones from either GET, POST, or PUT requests. Actually calling the API presents a JSON object with only the id field being defined:

❯ curl "http://localhost:8108/collections/products/synonyms/coat-synonyms" -X DELETE \
-H "Content-Type: application/json" \
-H "X-TYPESENSE-API-KEY: ${TYPESENSE_API_KEY}"

{"id":"coat-synonyms"}

Changes

• fix response schema for DELETE /collection/{collectionName}/synonyms/{synonymId} endpoint
• add missing SearchSynonymDeleteReponse schema definition

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