operator: Fix docs minio storage uses bucketnames instead of bucketname (#8116)

Fixes a typo in the documentation for the operator docs. for a
successful installation using bucketname will fail. Configuring the
secret with the key bucketnames should work.

operator/docs/lokistack/object_storage.md

@@ -130,7 +130,7 @@ Loki Operator supports [AWS S3](https://aws.amazon.com/), [Azure](https://azure.
 
     ```console
     kubectl create secret generic lokistack-dev-minio \
-      --from-literal=bucketname="<BUCKET_NAME>" \
+      --from-literal=bucketnames="<BUCKET_NAME>" \
       --from-literal=endpoint="<MINIO_BUCKET_ENDPOINT>" \
       --from-literal=access_key_id="<MINIO_ACCESS_KEY_ID>" \
       --from-literal=access_key_secret="<MINIO_ACCESS_KEY_SECRET>"