[HOTFIX] rename pytest's branch(master to main)

Author: dohyeop-sub

tox.ini

@@ -9,7 +9,7 @@ envlist=
 extras = testing
 deps =
   pytestlatest: pytest
-  pytestmaster: git+https://github.com/pytest-dev/pytest.git@master
+  pytestmaster: git+https://github.com/pytest-dev/pytest.git@main
 commands=
   pytest {posargs}