Better docs for flow control managers.

Author: Lukasa

HISTORY.rst

@@ -4,7 +4,8 @@ Release History
 X.X.X (XXXX-XX-XX)
 ------------------
 
-- Add logic for pluggable objects to manage the flow-control window.
+- Add logic for pluggable objects to manage the flow-control window for both
+  connections and streams.
 - Raise new ``HPACKDecodingError`` when we're unable to validly map a
   Huffman-encoded string.
 - Correctly respect the HPACK EOS character.