chore(deps): update dependency docker/buildx to v0.21.2 #10123

Job	Run time
ci / revisions	3s
ci / buildx / Build, bleeding, linux/arm64	9m 10s
ci / build / Build, bleeding, linux/amd64	6m 51s
ci / Trivy Container Scan	1m 53s
ci / Anchore Container Scan	1m 21s
ci / test-basic / Test container basic, bleeding	2m 49s
ci / Merge images, bleeding	27s
ci / test-saml / Test container saml, bleeding	2m 49s
ci / test-novolume / Test container read-write, bleeding	2m 44s
ci / test-single-celery / Test container celery-single, bleeding	2m 23s
ci / test-split / Test container split, bleeding	2m 32s
ci / test-ssl / Test container basic, bleeding	2m 42s
ci / test-localtime / Test container localtime, bleeding	3m 1s
ci / Tests, bleeding	1s
ci / Publish to GitHub, ${{ inputs.variant }}	0s
ci / Publish to Docker Hub, ${{ inputs.variant }}	0s
	38m 46s

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