build: no need for environment ranges when we want the setting all the time

Author: nedbat

tox.ini

@@ -31,14 +31,8 @@ setenv =
     pypy3{,10,11}: COVERAGE_TEST_CORES=pytrace
     # If we ever need a stronger way to suppress warnings:
     #PYTHONWARNINGS=ignore:removed in Python 3.14; use ast.Constant:DeprecationWarning
-    # We want to know about missing encoding arguments, but we need to silence
-    # some warnings that aren't ours.  We can't silence them in 3.9 because
-    # EncodingWarning doesn't exist yet, and it's hard to suppress them in some
-    # environments and not others.  So by default, don't warn, and we'll enable
-    # the warning in a handful of environments to catch the problems.
-    PYTHONWARNDEFAULTENCODING=
-    py3{10-15}: PYTHONWARNDEFAULTENCODING=1
-    py3{10-15}: PYTHONWARNINGS=ignore::EncodingWarning:pip._internal.utils.subprocess
+    PYTHONWARNDEFAULTENCODING=1
+    PYTHONWARNINGS=ignore::EncodingWarning:pip._internal.utils.subprocess
     # Disable CPython's color output
     PYTHON_COLORS=0