chore(main): release sdk 0.3.21 #6643

Job	Run time
go (examples)	1m 20s
image build	1m 36s
go (sdk)	2m 14s
go (service)	3m 21s
go (lib/ocrypto)	1m 19s
Protocol Buffer Lint and Gencode Up-to-date check	31s
go (lib/fixtures)	1m 0s
go (lib/flattening)	1m 7s
integration tests	5m 38s
license check	48s
otdfctl e2e tests	5m 34s
platform-xtest / cross-client-test	9m 20s
ci	1s
	33m 49s

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