Update pytest requirement from ~=6.2.3 to ~=6.2.4 (#71)

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@6.2.3...6.2.4)

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

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

Author: dependabot[bot]

requirements-dev.txt

@@ -9,7 +9,7 @@
 # setup.py.
 coverage ~=5.5
 flake8 ~=3.9.1
-pytest ~=6.2.3
+pytest ~=6.2.4
 ipython ~=7.23.0
 numpydoc ~=1.1.0
 sphinx ~=3.5.4