Bump cvxpy from 1.3.0 to 1.3.1 in /requirements (#806)

Bumps [cvxpy](https://github.com/cvxpy/cvxpy) from 1.3.0 to 1.3.1.
- [Release notes](https://github.com/cvxpy/cvxpy/releases)
- [Commits](https://github.com/cvxpy/cvxpy/compare/v1.3.0...v1.3.1)

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

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requirements/requirements.txt

@@ -1,7 +1,7 @@
 numpy == 1.24.2
 scipy == 1.10.1
 matplotlib == 3.7.1
-cvxpy == 1.3.0
+cvxpy == 1.3.1
 pytest == 7.2.2 # For unit test
 pytest-xdist == 3.2.1 # For unit test
 mypy == 1.1.1 # For unit test