Bump matplotlib from 3.9.2 to 3.9.3 in /requirements

Bumps [matplotlib](https://github.com/matplotlib/matplotlib) from 3.9.2 to 3.9.3.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.9.2...v3.9.3)

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

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

Author: dependabot[bot]

requirements/requirements.txt

@@ -1,6 +1,6 @@
 numpy == 2.1.3
 scipy == 1.14.1
-matplotlib == 3.9.2
+matplotlib == 3.9.3
 cvxpy == 1.5.3
 pytest == 8.3.4 # For unit test
 pytest-xdist == 3.6.1 # For unit test