packaging: Remove requirements/, deprecated by pyproject.toml (#507)

Author: tony

CHANGES

@@ -7,12 +7,18 @@ To install the unreleased libtmux version, see [developmental releases](https://
 ```console
 $ pip install --user --upgrade --pre libtmux
 ```
+
 ## libtmux 0.25.x (unreleased)
 
 - _Notes on upcoming releases will be added here_
 
 <!-- Maintainers and contributors: Insert change notes for the next release above -->
 
+### Packaging
+
+- Remove `requirements/` folder, which was unused and deprecated by
+  pyproject.toml (#507)
+
 ## libtmux 0.24.0 (2023-11-19)
 
 _Maintenance only, no bug fixes or new features_