docs: release notes for the v21.0.5 release #2824

Job	Run time
list	23s
workflow (modules-builder-tests)	1m 48s
workflow (build-cli)	1m 33s
workflow (devkit-core-tests-rerun)	1m 25s
workflow (devkit-core-tests)	1m 13s
workflow (build-unit-tests)	2m 21s
	8m 43s

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