CI use 6.1 nightlies #57

Job	Run time
Cxx interop / Construct Cxx interop matrix	3s
Unit tests / Construct unit test matrix	2s
Soundness / Documentation check	2m 27s
Soundness / License headers check	4s
Soundness / API breakage check	3m 21s
Soundness / Unacceptable language check	3s
Soundness / Broken symlinks check	2s
Soundness / Format check	35s
Soundness / Python lint check	8s
Soundness / Shell check	31s
Soundness / YAML lint check	3s
Unit tests / Unit tests / Linux (5.9)	4m 6s
Unit tests / Unit tests / Linux (5.10)	4m 7s
Unit tests / Unit tests / Linux (6.0)	4m 27s
Unit tests / Unit tests / Linux (nightly-6.1)	4m 54s
Unit tests / Unit tests / Linux (nightly-main)	5m 1s
Cxx interop / Cxx interop / Linux (5.9)	1m 56s
Cxx interop / Cxx interop / Linux (5.10)	2m 6s
Cxx interop / Cxx interop / Linux (6.0)	2m 7s
Cxx interop / Cxx interop / Linux (nightly-6.1)	2m 45s
Cxx interop / Cxx interop / Linux (nightly-main)	2m 32s
	41m 20s

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