Use proxy artifacts for `v2.21.1` #6805

Job	Run time
Multi-language repository (macos-latest, stable-v2.15.5)	9m 45s
Multi-language repository (ubuntu-latest, stable-v2.19.4)	4m 16s
Multi-language repository (macos-latest, stable-v2.16.6)	8m 53s
Multi-language repository (ubuntu-latest, stable-v2.16.6)	4m 0s
Multi-language repository (ubuntu-latest, default)	3m 50s
Multi-language repository (macos-latest, nightly-latest)	8m 39s
Multi-language repository (macos-latest, linked)	8m 4s
Multi-language repository (macos-latest, stable-v2.19.4)	9m 33s
Multi-language repository (macos-latest, default)	7m 46s
Multi-language repository (ubuntu-latest, stable-v2.15.5)	4m 0s
Multi-language repository (ubuntu-latest, stable-v2.17.6)	4m 19s
Multi-language repository (ubuntu-latest, linked)	3m 48s
Multi-language repository (macos-latest, stable-v2.17.6)	8m 20s
Multi-language repository (ubuntu-latest, stable-v2.18.4)	4m 16s
Multi-language repository (macos-latest, stable-v2.18.4)	7m 51s
Multi-language repository (ubuntu-latest, nightly-latest)	3m 45s
	1h 41m 5s

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