Bump github.com/onsi/ginkgo/v2 from 2.20.1 to 2.21.0 #34611

Job	Run time
Check whether tests need to be run based on diff	17s
Verify docs and spelling	42s
Unit test (ubuntu-latest)	7m 57s
Golangci-lint (ubuntu-latest)	8m 54s
Integration test	5m 56s
Unit test (windows-2022)	14m 25s
Build Antrea and antctl binaries	13m 7s
Golangci-lint (macos-latest)	9m 46s
Check tidy, code generation and manifest	4m 9s
Build Antrea Windows binaries	2m 13s
Go benchmark test	5m 8s
	1h 12m 34s

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