IrisDeprecation in netcdf saver

When running climix with gordias a IrisDeprecation message related to gordias is printed.

/home/sm_carni/.conda/envs/climix-patch/lib/python3.11/site-packages/iris/fileformats/netcdf/saver.py:2860: IrisDeprecation: Saving to netcdf with legacy-style attribute handling for backwards compatibility. This mode is deprecated since Iris 3.8, and will eventually be removed. Please consider enabling the new split-attributes handling mode, by setting 'iris.FUTURE.save_split_attrs = True'. warn_deprecated(message)