[Discover] Fix search session rename error in dev (#218363) (#226757)

## Summary

Closes #218363

Updating a search session returns an `updated_by` key that wasn't
defined in the `searchSessionsUpdateSchema`. While in dev the
`core_versioned_route` runs some response validations and was
complaining that the key wasn't defined there.

---

Before


https://github.com/user-attachments/assets/4e1afa28-6115-440f-84fb-4b524ea3b7b9

After


https://github.com/user-attachments/assets/d1ec9a7d-dfc7-4cdb-9891-9fe99c3fd2cf


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Author: AlexGPlay

src/platform/plugins/shared/data/server/search/routes/response_schema.ts

@@ -68,6 +68,7 @@ export const searchSessionsUpdateSchema = () =>
     id: schema.string(),
     type: schema.string(),
     updated_at: schema.maybe(schema.string()),
+    updated_by: schema.maybe(schema.string()),
     version: schema.maybe(schema.string()),
     namespaces: schema.maybe(schema.arrayOf(schema.string())),
     references: schema.maybe(referencesSchema),