Change default release version in GitHub action to `602.0.0` #158

Job	Run time
Run tests using swift-syntax-dev-utils (Linux)	23m 2s
Run tests using swift-syntax-dev-utils (Windows)	48m 28s
Validate generated code	2m 48s
Test / Linux (5.9 - jammy)	3m 49s
Test / Linux (5.10 - jammy)	3m 50s
Test / Linux (6.0 - jammy)	3m 58s
Test / Linux (6.1 - jammy)	3m 52s
Test / Linux (nightly-main - jammy)	4m 36s
Test / Windows (5.9 - windows-2022)	22m 38s
Test / Linux (nightly-6.1 - jammy)	4m 28s
Test / Windows (6.0 - windows-2022)	24m 28s
Test / Windows (6.1 - windows-2022)	20m 53s
Test / Windows (nightly - windows-2019)	15m 9s
Test / Windows (nightly-6.1 - windows-2019)	16m 18s
Soundness / API breakage check	0s
Soundness / Documentation check	4m 59s
Soundness / Unacceptable language check	3s
Soundness / Broken symlinks check	5s
Soundness / License headers check	20s
Soundness / Format check	38s
Soundness / Python lint check	8s
Soundness / Shell check	32s
Soundness / YAML lint check	4s
	3h 25m 6s

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