docs: release notes for the v21.2.5 release #3334

Job	Run time
list	26s
workflow (build-cli)	1m 42s
workflow (devkit-core-tests)	1m 24s
workflow (modules-builder-tests)	1m 56s
workflow (devkit-core-tests-rerun)	1m 28s
workflow (build-unit-tests)	2m 25s
	9m 21s

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