Change wording in data module doc following SHA256 -> MD5 change

Signed-off-by: Håkon Wiik Ånes <hwaanes@gmail.com>

doc/dev/adding_to_data_module.rst

@@ -6,10 +6,10 @@ Adding data to the data module
 Example datasets used in the documentation and tests are included in the
 :mod:`kikuchipy.data` module via the `pooch <https://www.fatiando.org/pooch/latest/>`__
 Python library. These are listed in a file registry (``kikuchipy.data._registry.py``)
-with their file verification string (hash, SHA256, obtain with e.g.
-``sha256sum <file>``) and location, the latter potentially not within the package but
-from the `kikuchipy-data <https://github.com/pyxem/kikuchipy-data>`__ repository or
-elsewhere, since some files are considered too large to include in the package.
+with their file verification string (hash, MD5, obtain with e.g. ``md5sum <file>``) and
+location, the latter potentially not within the package but from the `kikuchipy-data
+<https://github.com/pyxem/kikuchipy-data>`__ repository or elsewhere, since some files
+are considered too large to include in the package.
 
 If a required dataset isn't in the package, but is in the registry, it can be downloaded
 from the repository when the user passes ``allow_download=True`` to e.g.