Remove tox-gha-actions configuration

We removed the Tox plugin used on GHA earlier, but forgot about this section.

Author: bittner

tox.ini

@@ -1,5 +1,4 @@
 # Tox (https://tox.wiki/) - run tests in isolation using virtualenv.
-# Also contains config settings for tools that don't look into pyproject.toml.
 
 [tox]
 envlist =
@@ -12,20 +11,6 @@ envlist =
     docs
     clean
 
-[gh-actions]
-fail_on_no_env = True
-python =
-    3.5: py35
-    3.6: py36
-    3.7: py37
-    3.8: py38
-    3.9: py39
-    3.10: py310
-    3.11: py311
-    3.12: py312
-    pypy-3.8: pypy38
-    pypy-3.9: pypy39
-
 [testenv]
 description = Unit tests
 deps =