DOCSP-45314: Removed headers (#84)

* DOCSP-45314: Removed headers

* RR feedback

* EC feedback

(cherry picked from commit 2e96f85)

source/upgrade.txt

@@ -161,6 +161,13 @@ The v4.0 driver introduces the following breaking changes to the API:
   library equivalents. For context, see the :ref:`Build System Breaking Changes
   <version-4.0-build-system-breaking>` section.
 
+- Removes the following header files:
+
+  - ``<bsoncxx/stdx/make_unique.hpp>``
+  - ``<bsoncxx/types/value.hpp>``
+  - ``<bsoncxx/util/functor.hpp>``
+  - ``<mongocxx/options/create_collection.hpp>``
+
 - Removes the following deprecated ``utf8`` types and functions that have ``string`` equivalents:
 
   - ``k_utf8`` from the ``bsoncxx::v_noabi::type`` class. Instead, use ``k_string``.