s/which/that/

Which is usually for descriptive clauses in technical writing, while
that is restrictive. Most of the time we are being being restrictive.
diff --git a/docs/hazmat/primitives/cryptographic-hashes.rst b/docs/hazmat/primitives/cryptographic-hashes.rst
index 3834737..6c56aca 100644
--- a/docs/hazmat/primitives/cryptographic-hashes.rst
+++ b/docs/hazmat/primitives/cryptographic-hashes.rst
@@ -56,7 +56,7 @@
         :meth:`finalize` and get an intermediate digest value while we continue
         to call :meth:`update` on the original.
 
-        :return: A new instance of :class:`Hash` which can be updated
+        :return: A new instance of :class:`Hash` that can be updated
             and finalized independently of the original instance.
         :raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize`