Add changelog entry

Author: aclark4life

doc/changelog.rst

@@ -17,6 +17,8 @@ PyMongo 4.16 brings a number of changes including:
 - Fixed return type annotation for ``find_one_and_*`` methods on :class:`~pymongo.asynchronous.collection.AsyncCollection`
   and :class:`~pymongo.synchronous.collection.Collection` to include ``None``.
 - Added support for NumPy 1D-arrays in :class:`bson.binary.BinaryVector`.
+- Fixed a bug in :class:`~pymongo.encryption.ClientEncryption`: ClientEncryption
+  shouldn't try to load mongo crypt shared library.
 
 Changes in Version 4.15.5 (2025/XX/XX)
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