Add fix to diff docstring to changelog

Author: ndgrigorian

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Use pybind11=2.13.6 [gh-1845](https://github.com/IntelPython/dpctl/pull/1845)
 * Remove unnecessary include in C++ header file [gh-1846](https://github.com/IntelPython/dpctl/pull/1846)
 * Build translation unit "simplify_iteration_space.cpp" compiled multiple times as a static library [gh-1847](https://github.com/IntelPython/dpctl/pull/1847)
+* Fix warning in documentation generation caused by `diff` docstring [gh-1855](https://github.com/IntelPython/dpctl/pull/1855)
 
 ## [0.18.0] - Sept. XX, 2024