Remove, redirect retrievers examples page (elastic#2233)

- Closes elastic/developer-docs-team#324
- Depends on elastic/elasticsearch#131766

Author: leemthompo

redirects.yml

@@ -290,3 +290,5 @@ redirects:
   # Related to https://github.com/elastic/docs-content/pull/2097
   'explore-analyze/machine-learning/machine-learning-in-kibana/xpack-ml-anomalies.md': 'explore-analyze/machine-learning/anomaly-detection.md'
   'explore-analyze/machine-learning/machine-learning-in-kibana/xpack-ml-dfa-analytics.md': 'explore-analyze/machine-learning/data-frame-analytics.md'
+
+  'solutions/search/retrievers-examples.md': 'elasticsearch://reference/elasticsearch/rest-apis/retrievers/retrievers-examples.md'