DOCSP-43918 - Removed APIs (#243)

Author: mongoKart

source/upgrade/v3.txt

@@ -61,6 +61,11 @@ Version 3.0 Breaking Changes
   and {+mdb-server+} versions, visit the
   :ref:`Compatibility <csharp-compatibility-tables>` page.
 
+- The classes, methods, and properties in the ``MongoDB.Driver.Core`` namespace that were
+  deprecated in v{+last-version-2-number+} are marked ``internal``. If the driver
+  provides a replacement for a deprecated class, method, or property, the compiler
+  messages in v{+last-version-2-number+} will display it.
+
 - The driver drops support for the
   ``MONGODB-CR`` authentication mechanism. To learn more about
   configuring authentication in the {+driver-short+}, see