build(deps): bump matplotlib from 3.8.1 to 3.9.4

Bumps [matplotlib](https://github.com/matplotlib/matplotlib) from 3.8.1 to 3.9.4.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.8.1...v3.9.4)

---
updated-dependencies:
- dependency-name: matplotlib
  dependency-version: 3.9.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -1,7 +1,7 @@
 h5py == 3.9.0
 jupyter == 1.0.0
 keras == 2.14.0
-matplotlib == 3.8.1
+matplotlib == 3.9.4
 notebook == 7.1.1
 numpy == 1.25.2
 pandas == 2.2.0