build(deps): bump matplotlib from 3.9.0 to 3.9.1

Bumps [matplotlib](https://github.com/matplotlib/matplotlib) from 3.9.0 to 3.9.1.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.9.0...v3.9.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -1,4 +1,4 @@
 astropy==6.1.1
-matplotlib==3.9.0
+matplotlib==3.9.1
 numpy==2.0.0
 scipy==1.14.0