Drop temporary workaround for get_codec (#361)

* Drop temporary workaround for `get_codec`

This workaround was added because `get_codec` was modifying its
argument. However as of Numcodecs 0.6.0, `get_codec` does not modify its
argument as it takes a copy and modifies the copy instead. Given as we
now require Numcodecs 0.6.0, this workaround is no longer needed. Hence
we drop it.

* Link this to the Numcodecs upgrade release note

Author: jakirkham

docs/release.rst

@@ -29,8 +29,8 @@ Bug fixes
 
 * The required version of the `numcodecs <http://numcodecs.rtfd.io>`_ package has been upgraded 
   to 0.6.2, which has enabled some code simplification and fixes a failing test involving
-  msgpack encoding. By :user:`John Kirkham <jakirkham>`, :issue:`360`, :issue:`352`, :issue:`355`,
-  :issue:`324`.
+  msgpack encoding. By :user:`John Kirkham <jakirkham>`, :issue:`361`, :issue:`360`, :issue:`352`,
+  :issue:`355`, :issue:`324`.
 
 * Failing tests related to pickling/unpickling have been fixed. By :user:`Ryan Williams <ryan-williams>`,
   :issue:`273`, :issue:`308`.

zarr/core.py

@@ -166,9 +166,6 @@ def _load_metadata_nosync(self):
             if config is None:
                 self._compressor = None
             else:
-                # temporary workaround for
-                # https://github.com/zarr-developers/numcodecs/issues/78
-                config = dict(config)
                 self._compressor = get_codec(config)
 
             # setup filters