Add missing QueryExpander and MultiQuery retrievers to version-2.21 sidebar (#10206)

Author: dfokina

docs-website/versioned_sidebars/version-2.21-sidebars.json

@@ -456,6 +456,13 @@
             "pipeline-components/preprocessors/textcleaner"
           ]
         },
+        {
+          "type": "category",
+          "label": "Query",
+          "items": [
+            "pipeline-components/query/queryexpander"
+          ]
+        },
         {
           "type": "category",
           "label": "Rankers",
@@ -513,6 +520,8 @@
             "pipeline-components/retrievers/inmemoryembeddingretriever",
             "pipeline-components/retrievers/mongodbatlasembeddingretriever",
             "pipeline-components/retrievers/mongodbatlasfulltextretriever",
+            "pipeline-components/retrievers/multiqueryembeddingretriever",
+            "pipeline-components/retrievers/multiquerytextretriever",
             "pipeline-components/retrievers/opensearchbm25retriever",
             "pipeline-components/retrievers/opensearchembeddingretriever",
             "pipeline-components/retrievers/opensearchhybridretriever",