Enable Swift 6.1 jobs in CI #106

Job	Run time
Cxx interop / Construct Cxx interop matrix	4s
Unit tests / Construct unit test matrix	3s
Soundness / API breakage check	44s
Soundness / Documentation check	43s
Soundness / Unacceptable language check	3s
Soundness / Broken symlinks check	3s
Soundness / Format check	33s
Soundness / License headers check	3s
Soundness / Shell check	30s
Soundness / Python lint check	5s
Soundness / YAML lint check	3s
Static SDK / Static SDK / Linux (latest-release Jammy)	55s
Static SDK / Static SDK / Linux (main Jammy)	53s
Unit tests / Unit tests / Linux (5.9)	58s
Unit tests / Unit tests / Linux (5.10)	58s
Unit tests / Unit tests / Linux (6.0)	58s
Unit tests / Unit tests / Linux (6.1)	59s
Unit tests / Unit tests / Linux (nightly-next)	59s
Unit tests / Unit tests / Linux (nightly-main)	59s
Cxx interop / Cxx interop / Linux (5.9)	53s
Cxx interop / Cxx interop / Linux (5.10)	54s
Cxx interop / Cxx interop / Linux (6.0)	53s
Cxx interop / Cxx interop / Linux (6.1)	53s
Cxx interop / Cxx interop / Linux (nightly-next)	52s
Cxx interop / Cxx interop / Linux (nightly-main)	53s
	15m 51s

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