Mention on_member_ban event change.

docs/migrating.rst

@@ -504,6 +504,19 @@ After: ::
 
 The first argument is now the :class:`Guild` that the emojis were updated from.
 
+The :func:`on_member_ban` event has received an argument change as well:
+
+Before: ::
+
+    async def on_member_ban(member)
+
+After: ::
+
+    async def on_member_ban(guild, user)
+
+As part of the change, the event can either receive a :class:`User` or :class:`Member`. To help in the cases that have
+:class:`User`, the :class:`Guild` is provided as
+
 The ``on_channel_`` events have received a type level split (see :ref:`migrating_1_0_channel_split`).
 
 Before: