Update changelog for v3.28.21 #9876

Job	Run time
check-codeql-versions	50s
analyze-actions	1m 3s
analyze-javascript (ubuntu-22.04)	4m 4s
analyze-javascript (windows-2022)	5m 23s
analyze-javascript (ubuntu-24.04)	3m 59s
analyze-javascript (ubuntu-24.04, linked)	4m 17s
analyze-javascript (windows-2022, linked)	7m 35s
analyze-javascript (ubuntu-22.04, linked)	4m 13s
analyze-javascript (macos-13)	8m 10s
analyze-javascript (windows-2025)	5m 35s
analyze-javascript (windows-2025, linked)	6m 20s
analyze-javascript (macos-14)	7m 10s
analyze-javascript (macos-14, linked)	7m 55s
analyze-javascript (macos-15, linked)	7m 54s
analyze-javascript (macos-15)	9m 20s
analyze-javascript (macos-13, linked)	11m 50s
	1h 35m 38s

Provide feedback