chore(security): removing unmaintained es7 upgrade proces (#7790)

Author: david-leifker

contrib/elasticsearch/es7-upgrade/Dockerfile

@@ -508,7 +508,6 @@ module.exports = {
             "docker/datahub-upgrade/README",
             "docs/advanced/no-code-modeling",
             "datahub-web-react/src/app/analytics/README",
-            "docs/advanced/es-7-upgrade",
             "docs/how/migrating-graph-service-implementation",
             "docs/advanced/field-path-spec-v2",
             "metadata-ingestion/adding-source",

contrib/elasticsearch/es7-upgrade/transfer.py

@@ -13,6 +13,8 @@ This file documents any backwards-incompatible changes in DataHub and assists pe
 ### Potential Downtime
 
 ### Deprecations
+- The docker image and script for updating from Elasticsearch 6 to 7 is no longer being maintained and will be removed from the `/contrib` section of
+the repository. Please refer to older releases if needed.
 
 ### Other notable Changes