remove elasticsearch support (#504)

Author: Phil Varner

.npm-upgrade.json

@@ -4,13 +4,9 @@
       "versions": "^2",
       "reason": "deprecated feature, leave as-is"
     },
-    "@elastic/elasticsearch": {
-      "versions": "^8",
-      "reason": "deprecated feature, leave as-is"
-    },
     "@types/node": {
       "versions": "^18",
       "reason": "using 16"
     }
   }
-}
+}

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased] - TBD
 
+### Removed
+
+- Elasticsearch is no longer supported as a backend. Only OpenSearch is now supported.
+
 ### Added
 
 - Publish ingest results to a post-ingest SNS topic