Bump pytest from 7.3.0 to 7.3.1 in /requirements (AtsushiSakai#818)

Bumps [pytest](https://github.com/pytest-dev/pytest) from 7.3.0 to 7.3.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@7.3.0...7.3.1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements/requirements.txt

@@ -2,7 +2,7 @@ numpy == 1.24.3
 scipy == 1.10.1
 matplotlib == 3.7.1
 cvxpy == 1.3.1
-pytest == 7.3.0 # For unit test
+pytest == 7.3.1 # For unit test
 pytest-xdist == 3.2.1 # For unit test
 mypy == 1.2.0 # For unit test
 ruff == 0.0.263 # For unit test