Bump pytest from 6.1.2 to 6.2.1 (#672)

Author: dependabot[bot]

requirements/requirements_dev.txt

@@ -10,7 +10,7 @@ hypothesis==5.43.3
 placebo==0.9.0
 pre-commit==2.9.3
 pylint==2.6.0
-pytest==6.1.2
+pytest==6.2.1
 pytest-black==0.3.12
 pytest-cov==2.10.1
 pytest-datadir==1.3.1