Remove wrong changelog about default Python version in the image (apa…

…che#36777)

In apache#36003 we **thought** we changed default "version" image to
point to "newest" python version not to the "oldest" supported
one - as agreed in https://lists.apache.org/thread/0oxnvct24xlqsj76z42w2ttw2d043oy3

However as observed and tracked in apache#36740 the change was not effective.
We only changed the moment at which latest image is pointing to
2.8.0 but not whether 2.8.0 points to `python-3.8` or `python-3.11'.

This means that we should only do that change for Python 3.9 qnd
revert the changelog (and cherry-pick it to 2.8.1)

docs/docker-stack/changelog.rst

@@ -53,14 +53,6 @@ Airflow 2.8
      working with ``Debian Bookworm``. While all reference images of Airflow 2.8.0 are built on ``Debian Bookworm``,
      it is still possible to build deprecated custom ``Debian Bullseye`` based image in 2.8.0 following the
 
-   * The "latest" image (i.e. default Airflow image when ``apache/airflow`` is used or
-     ``apache/airflow:slim-latest``) uses now the newest supported Python version. Previously it was using
-     the "default" Python version which was Python 3.8 as of Airflow 2.7. With Airflow reference images
-     released for Airflow 2.8.0, the images are going to use Python 3.11 as this is the latest supported
-     version for Airflow 2.8 line. Users can use Python 3.8 by using ``apache/airflow:2.8.0-python3.8`` and
-     ``apache/airflow:slim-2.8.0-python-3.8`` images respectively so while the change is potentially
-     breaking, it is very easy to switch to the previous behaviour.
-
    * By default the images now have "MariaDB" client installed. Previous images had "MySQL" client installed.
      The MariaDB client is a drop-in replacement for "MySQL" one and is compatible with MySQL. This might
      be a breaking change for users who used MySQL client in their images, however those should be very