Update _index.md (#4553)

fix missing `s` in `default`

Author: savar

docs/sources/helm-charts/tempo-distributed/get-started-helm-charts/_index.md

@@ -480,7 +480,7 @@ The following example configuration sets some global configuration options, as w
 
 ```yaml
 global_overrides:
-    default:
+    defaults:
         ingestion:
           rate_limit_bytes: 5 * 1000 * 1000
           burst_size_bytes: 5 * 1000 * 1000