[8.0][DOCS] Backports redirects. (#6675)

Author: szabosteve

docs/redirects.asciidoc

@@ -11,4 +11,14 @@ This page has moved. See <<configuration>>.
 [role="exclude",id="nest"]
 == NEST - High level client
 
+This page has been deleted.
+
+[role="exclude",id="indexing-documents"]
+== Indexing documents
+
+This page has been deleted.
+
+[role="exclude",id="bulkall-observable"]
+== Multiple documents with `BulkAllObservable` helper
+
 This page has been deleted.