[Backport 8.15] Added/updated snippets for docs (#2319)

(cherry picked from commit f737290d10)

Co-authored-by: Josh Mock <joshua.mock@elastic.co>

docs/doc_examples/640e4f2c2d29f9851320a70927bd7a6c.asciidoc

@@ -0,0 +1,12 @@
+// This file is autogenerated, DO NOT EDIT
+// Use `node scripts/generate-docs-examples.js` to generate the docs examples
+
+[source, js]
+----
+const response = await client.cluster.putSettings({
+  persistent: {
+    "indices.lifecycle.poll_interval": null,
+  },
+});
+console.log(response);
+----