change hardcoded master branch in readme enumeration to HEAD

diff --git a/RelNotes b/RelNotes
index fdd7e420b1999e89f35a245b225a263bf5c1fd9d..fc657e7d2f4b22ce71b2983bd33d9fca131c0c37 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/2.16.3.txt
\ No newline at end of file
+Documentation/RelNotes/2.24.0.txt
\ No newline at end of file