[e2e tests] Remove explicit sleep command for toolbox containers (#6021) #31720

Job	Run time
Check whether tests need to be run based on diff	23s
Verify docs and spelling	32s
Unit test (windows-2022)	12m 21s
Integration test	9m 37s
Golangci-lint (ubuntu-latest)	7m 20s
Unit test (ubuntu-latest)	6m 12s
Golangci-lint (macos-latest)	11m 24s
Build Antrea and antctl binaries	9m 38s
Check tidy, code generation and manifest	5m 29s
Build Antrea Windows binaries	1m 47s
Go benchmark test	4m 25s
	1h 9m 8s

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