Minor tweaks in RELEASE_NOTES.txt

Author: garydgregory

RELEASE_NOTES.txt

@@ -27,8 +27,8 @@ Change Log
   window to the max value (ported from 5.3.x; omitted by mistake).
   Contributed by Oleg Kalnichevski <olegk at apache.org>
 
-* Ensure async data consumers can avoid NPE if they have been canceled / released from another
-  thread at the same with concurrent data processing
+* Ensure async data consumers can avoid NPE if they have been canceled or released from another
+  thread at the same with concurrent data processing.
   Contributed by Oleg Kalnichevski <olegk at apache.org>
 
 * Fixed connection pool lease timeout race potentially causing pool entry leak (#649).