CI use 6.1 nightlies #61

Job	Run time
Cxx interop / Construct Cxx interop matrix	2s
Unit tests / Construct unit test matrix	4s
Soundness / Documentation check	2m 11s
Soundness / API breakage check	2m 22s
Soundness / Broken symlinks check	3s
Soundness / Format check	31s
Soundness / License headers check	3s
Soundness / Python lint check	4s
Soundness / Shell check	29s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	4s
Cxx interop / Cxx interop / Linux (5.9)	1m 25s
Cxx interop / Cxx interop / Linux (5.10)	1m 23s
Cxx interop / Cxx interop / Linux (6.0)	1m 37s
Cxx interop / Cxx interop / Linux (nightly-6.1)	1m 58s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 53s
Unit tests / Unit tests / Linux (5.9)	2m 53s
Unit tests / Unit tests / Linux (5.10)	2m 51s
Unit tests / Unit tests / Linux (6.0)	3m 8s
Unit tests / Unit tests / Linux (nightly-6.1)	3m 15s
Unit tests / Unit tests / Linux (nightly-main)	3m 9s
	29m 28s

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