CI: Remove unused no longer needed PYTHONWARNINGS

tox.ini

@@ -25,7 +25,7 @@ deps =
 extras =
     test
 setenv =
-    PYTHONWARNINGS = all,ignore::ImportWarning:importlib._bootstrap_external,ignore::DeprecationWarning:site,ignore::DeprecationWarning:distutils,ignore::DeprecationWarning:pip._vendor.packaging.version
+    PYTHONWARNINGS = all
     PYTEST_ADDOPTS = {env:PYTEST_ADDOPTS:} --color yes
 commands=
     python -X dev -m pytest --durations 25 {posargs}