Bump Core version to 21.0.0rc2 #2

Job	Run time
Integration tests (ubuntu-20.04, 1.22, 20)	17m 15s
Unit tests (ubuntu-20.04, 1.22)	3m 33s
Unit tests (ubuntu-22.04, 1.22)	3m 38s
Build (ubuntu-latest, x86_64-unknown-linux-gnu, amd64)	2m 24s
Build (ubuntu-latest, aarch64-unknown-linux-gnu, arm64)	2m 57s
Integration tests (ubuntu-20.04, 1.22, 21)	17m 46s
Integration tests (ubuntu-22.04, 1.22, 20)	18m 10s
Build (macos-latest, x86_64-apple-darwin, amd64)	2m 6s
Integration tests (ubuntu-22.04, 1.22, 21)	18m 2s
Build (macos-latest, aarch64-apple-darwin, arm64)	2m 35s
Build (windows-latest, x86_64-pc-windows-gnu, amd64)	14m 11s
	1h 42m 37s

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