Update release history

docs/releasehistory.md

@@ -6,12 +6,15 @@ Releases follow the `major.minor.micro` scheme recommended by [PEP440](https://w
 * `minor` increments add features but do not break API compatibility
 * `micro` increments represent bugfix releases or improvements in documentation
 
-## Current development
+## 0.16.5
 
 ### Improved warnings and documentation
 
 - [PR #1939](https://github.com/openforcefield/openff-toolkit/pull/1939): Resolves [#1587](https://github.com/openforcefield/openff-toolkit/pull/1587) by emitting a warning when from_openeye or from_rdkit try to load a molecule with multiple disconnected components. 
 
+### Miscellaneous
+
+- [PR #1940](https://github.com/openforcefield/openff-toolkit/pull/1940): Fixes an esoteric issue in which optional upstream packages resulted in import errors.
 
 ## 0.16.4