resetwarnings(): change the docstring to reflect what the code

actually does.  Note that the description in the Library Reference
manual is already accurate.

Bugfix candidate.

Lib/warnings.py

@@ -139,7 +139,7 @@ def filterwarnings(action, message="", category=Warning, module="", lineno=0,
         filters.insert(0, item)
 
 def resetwarnings():
-    """Reset the list of warnings filters to its default state."""
+    """Clear the list of warning filters, so that  no filters are active."""
     filters[:] = []
 
 class _OptionError(Exception):