Update matplotlib requirement from ~=3.8.4 to ~=3.9.0 in the major group

Updates the requirements on [matplotlib](https://github.com/matplotlib/matplotlib) to permit the latest version.

Updates `matplotlib` to 3.9.0
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](https://github.com/matplotlib/matplotlib/compare/v3.8.4...v3.9.0

)

---
updated-dependencies:
- dependency-name: matplotlib
  dependency-type: direct:development
  dependency-group: major
...
Signed-off-by: dependabot[bot] <support@github.com>

requirements-dev.txt

@@ -6,4 +6,4 @@ wheel~=0.43.0
 lion-pytorch~=0.1.4
 scipy~=1.13.0
 pandas~=2.2.2
-matplotlib~=3.8.4
+matplotlib~=3.9.0