bpo-14014: Clarify StreamWriter.reset() documentation (GH-13716)

diff --git a/Doc/library/codecs.rst b/Doc/library/codecs.rst
index a026513..3169ae5 100644
--- a/Doc/library/codecs.rst
+++ b/Doc/library/codecs.rst
@@ -697,7 +697,7 @@
 
    .. method:: reset()
 
-      Flushes and resets the codec buffers used for keeping state.
+      Resets the codec buffers used for keeping internal state.
 
       Calling this method should ensure that the data on the output is put into
       a clean state that allows appending of new fresh data without having to
@@ -792,7 +792,7 @@
 
    .. method:: reset()
 
-      Resets the codec buffers used for keeping state.
+      Resets the codec buffers used for keeping internal state.
 
       Note that no stream repositioning should take place. This method is
       primarily intended to be able to recover from decoding errors.