Increase swift tools version to 5.9 #76

Job	Run time
Validate generated code	3m 0s
Run tests using swift-syntax-dev-utils (Windows)	49m 44s
Run tests using swift-syntax-dev-utils (Linux)	24m 26s
Test / Linux (5.9 - jammy)	3m 54s
Test / Linux (5.10 - jammy)	3m 52s
Test / Linux (6.0 - jammy)	4m 2s
Test / Windows (5.9 - windows-2022)	27m 8s
Test / Linux (nightly-main - jammy)	4m 48s
Test / Windows (6.0 - windows-2022)	27m 18s
Soundness / API breakage check	0s
Soundness / Documentation check	1m 16s
Soundness / Unacceptable language check	4s
Soundness / License headers check	10s
Soundness / Broken symlinks check	5s
Soundness / Format check	37s
Soundness / Shell check	34s
Soundness / YAML lint check	2s
Soundness / Python lint check	5s
Test / Linux (nightly-6.1 - jammy)	5m 2s
Test / Windows (nightly - windows-2019)	16m 23s
Test / Windows (nightly-6.1 - windows-2019)	16m 35s
	3h 9m 5s

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