Add note and fix flush call.

lib/async/io/stream.rb

@@ -47,6 +47,8 @@ def initialize(io, block_size: BLOCK_SIZE, maximum_read_size: MAXIMUM_READ_SIZE,
 				@eof = false
 
 				@pending = 0
+				# This field is ignored, but used to mean, try to buffer packets in a single iteration of the reactor.
+				# @deferred = deferred
 
 				@writing = Async::Semaphore.new(1)
 

spec/async/io/stream_spec.rb

@@ -83,7 +83,7 @@
 
 				task = reactor.async do
 					output.write("Hello World")
-					output.flush(deferred: true)
+					output.flush
 				end
 
 				expect do