Updated the latest review date for the abbreviated list of release note in the README file

Signed-off-by: Yixin Zhang <[email protected]>

Author: Yixin Zhang

README

@@ -118,7 +118,7 @@ The rest of this README file contains:
 ===========================================================================
 
 The following abbreviated list of release notes applies to this code
-base as of this writing (March 2019):
+base as of this writing (April 2020):
 
 General notes
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