fix readme note formatting

Author: miguelgrinberg

README

@@ -1,12 +1,24 @@
 Elasticsearch DSL
 =================
 
-> [!NOTE]
-> As of release 9.0, Elasticsearch DSL is part of the official Elasticsearch
-> client for Python, so a separate install is not needed. To migrate, just
-> replace `elasticsearch_dsl` with `elasticsearch.dsl` in all imports.
->
-> The following instructions apply to versions 8 and older.
+Deprecation notice
+------------------
+
+As of release 8.18.0, the Elasticsearch DSL package is part of the official
+`Elasticsearch Python client <https://github.com/elastic/elasticsearch-py>`_,
+so a separate install is not needed. To migrate, follow these steps:
+
+- Uninstall the ``elasticsearch-dsl`` package
+- Make sure you have version 8.18.0 or newer of the ``elasticsearch`` package
+  installed
+- Replace ``elasticsearch_dsl`` with ``elasticsearch.dsl`` in your imports (the
+  underscore of the legacy package name should be replaced with a period).
+
+The following instructions only apply to versions 8.17 and older of this
+package.
+
+Introduction
+------------
 
 Elasticsearch DSL is a high-level library whose aim is to help with writing and
 running queries against Elasticsearch. It is built on top of the official