Update pytest requirement from ~=5.4.3 to ~=6.0.1 (#612)

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/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@5.4.3...6.0.1)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

requirements-dev.txt

@@ -1,7 +1,7 @@
 coverage ~=5.2
 doctr ~=1.8.0
 pyflakes ~=2.2.0
-pytest ~=5.4.3
+pytest ~=6.0.1
 vcrpy ~=4.1.0
 doctr ~=1.8.0
 ipython ~=7.16.1