Bump pytest from 4.3.0 to 6.1.2

Bumps [pytest](https://github.com/pytest-dev/pytest) from 4.3.0 to 6.1.2.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@4.3.0...6.1.2)

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

requirements-test.txt

@@ -1,6 +1,6 @@
 cython
 numpy
 -e .
-pytest==4.3.0
+pytest==6.1.2
 pytest-cov
 coveralls