update changelog

Author: gabis-precog

CHANGELOG.rst

@@ -8,6 +8,7 @@ v0.4.3
 - Added on_ready callback to RSocketServer. Called when sender/receiver tasks are ready
 - Implement ReactiveX (3.0, 4.0) server side handler. Allows to define RequestHandler directly using ReactiveX
 - Added sending_done_event argument to request_channel to allow client to wait until sending to server is complete/canceled
+- Removed RSocketBase class dependency from RequestHandler. It is not longer required as an argument to __init__
 
 v0.4.2
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