Update CHANGELOG

Author: marcovtwout

CHANGELOG

@@ -4,7 +4,7 @@
 Version 1.1.28 under development
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-- No changes yet
+- Bug #4497: PHP 8.1 compatibility: Fix unserialize null in CRedisCache (kenguest, wtommyw)
 
 Version 1.1.27 November 21, 2022
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