build(poetry): upgrade pytest to ^7.0.0

pytest-regression now depends on higher version of pytest
ESSS/pytest-regressions#107

Author: Lee-W

pyproject.toml

@@ -75,7 +75,7 @@ charset-normalizer = "^2.1.0"
 [tool.poetry.dev-dependencies]
 ipython = "^7.2"
 # test
-pytest = "^6.2.5"
+pytest = "^7.0.0"
 pytest-cov = "^2.6"
 pytest-mock = "^2.0"
 codecov = "^2.0"