Update pytest requirement from ~=8.1 to ~=8.3 in /kerngen (#29)

Updates the requirements on [pytest](https://github.com/pytest-dev/pytest) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@8.1.0...8.3.2)

---
updated-dependencies:
- dependency-name: pytest
  dependency-type: direct:production
...

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

kerngen/requirements.txt

@@ -6,4 +6,4 @@ black ~= 24.3
 pylint ~= 3.1
 
 # for testing
-pytest ~= 8.1
+pytest ~= 8.3