Bump matplotlib from 3.8.4 to 3.9.1

Bumps [matplotlib](https://github.com/matplotlib/matplotlib) from 3.8.4 to 3.9.1.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.8.4...v3.9.1)

---
updated-dependencies:
- dependency-name: matplotlib
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

setup.py

@@ -32,7 +32,7 @@
     keywords='pyiron',
     packages=find_packages(exclude=["*tests*"]),
     install_requires=[
-        'matplotlib==3.8.4',
+        'matplotlib==3.9.1',
         'numpy==1.26.4',
         'pyiron_base==0.9.5',
         'pyiron_snippets==0.1.2',