tox.ini: Remove some redundant lists of python versions

tox.ini

@@ -23,14 +23,6 @@ envlist =
 
 [testenv]
 basepython =
-           py3: python3
-           py39: python3.9
-           py310: python3.10
-           py311: python3.11
-           py312: python3.12
-           py313: python3.13
-           py314: python3.14
-           pypy3: pypy3
            # In theory, it doesn't matter which python version is used here.
            # In practice, things like changes to the ast module can alter
            # the outputs of the tools (especially where exactly the
@@ -61,7 +53,7 @@ setenv =
        # during sdist installation (and it doesn't seem to be
        # possible to set environment variables during that phase of
        # tox).
-       {py3,py39,py310,py311,py312,py313,py314,pypy3}: PYTHONWARNINGS=error:::tornado
+       PYTHONWARNINGS=error:::tornado
        # Warn if we try to open a file with an unspecified encoding.
        # (New in python 3.10, becomes obsolete when utf8 becomes the
        # default in 3.15)