Doc: Explicitly specify Py 3.10 will be supported from Airflow 2.3.0 (#…

…22602)

Based on the feedback in #19059 (comment) -- this PR makes it explicit

README.md

@@ -104,7 +104,8 @@ MariaDB is not tested/recommended.
 **Note**: SQLite is used in Airflow tests. Do not use it in production. We recommend
 using the latest stable version of SQLite for local development.
 
-**Note**: Python v3.10 is not supported yet. For details, see [#19059](https://github.com/apache/airflow/issues/19059).
+**Note**: Support for Python v3.10 will be available from Airflow 2.3.0. The `main` (development) branch
+already supports Python 3.10.
 
 **Note**: Airflow currently can be run on POSIX-compliant Operating Systems. For development it is regularly
 tested on fairly modern Linux Distros and recent versions of MacOS.