removed config section

Author: jhamman

docs/user-guide/v3_migration.rst

@@ -162,30 +162,6 @@ When installing using ``pip``:
 - The ``jupyter`` optional dependency group has been removed, since v3 contains no
    jupyter specific functionality.
 
-Configuration
-~~~~~~~~~~~~~
-
-There is a new configuration system based on `donfig <https://github.com/pytroll/donfig>`_,
-which can be accessed via ``zarr.config`` (see :ref:`user-guide-config` for more information)
-Configuration values can be set using code like the following:
-
-.. code-block:: python
-
-   import zarr
-   zarr.config.set({"array.order": "F"})
-
-Alternatively, configuration values can be set using environment variables,
-e.g. ``ZARR_ARRAY__ORDER=F``.
-
-Configuration options include the following:
-
-- Default Zarr format ``default_zarr_version``
-- Default array order in memory ``array.order``
-- Default codecs ``array.v3_default_codecs`` and ``array.v2_default_compressor``
-- Whether empty chunks are written to storage ``array.write_empty_chunks``
-- Async and threading options, e.g. ``async.concurrency`` and ``threading.max_workers``
-- Selections of implementations of codecs, codec pipelines and buffers
-
 Miscellaneous
 ~~~~~~~~~~~~~