DOC: clarify that previous default value was False

Author: toobaz

pandas/core/series.py

@@ -3814,8 +3814,8 @@ def to_csv(self, *args, **kwargs):
         if kwargs.get("header", None) is None:
             warnings.warn("The signature of `Series.to_csv` was aligned "
                           "to that of `DataFrame.to_csv`, and argument "
-                          "'header' will change its default value to "
-                          "True: please pass an explicit value to suppress "
+                          "'header' will change its default value from False "
+                          "to True: please pass an explicit value to suppress "
                           "this warning.", warning_klass,
                           stacklevel=stack_level)
             kwargs["header"] = False  # Backwards compatibility.