release: cut the v21.2.6 release #10138

Job	Run time
build	2m 50s
build-e2e-windows	2m 50s
lint	2m 8s
Browser Compatibility Tests	1s
publish-snapshots	1s
test	1s
e2e-package-managers	1s
e2e	1s
e2e-snapshots	1s
e2e-windows	1s
	7m 55s

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