Correct release note for v1.5.1

Author: hu

README.md

@@ -44,7 +44,7 @@ This library is licensed under the Amazon Software License.
 
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 ### Release notes
-#### Release 1.5.1 (24th Aug 2018)
+#### Release 1.5.1 (28th Sep 2018)
 * Fragment Metadata Support for Producer SDK
 * Add fallback frame rate to avoid negotiation issue on certain machines like macbook air