Update pytest requirement from ~=7.4 to ~=8.1

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@7.4.0...8.1.0)

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

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

requirements/requirements_testing.txt

@@ -1,4 +1,4 @@
 codecov~=2.1
-pytest~=7.4
+pytest~=8.1
 pytest-cov~=4.1
 pytest-tornasync~=0.6.0.post2