Rename nightly_6_1 params to nightly_next #95

Job	Run time
Unit tests / Construct unit test matrix	3s
Cxx interop / Construct Cxx interop matrix	5s
Soundness / API breakage check	4m 15s
Soundness / Broken symlinks check	2s
Soundness / Documentation check	2m 51s
Soundness / Format check	36s
Soundness / License headers check	4s
Soundness / Python lint check	5s
Soundness / Shell check	35s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	2s
Unit tests / Unit tests / Linux (5.9)	4m 39s
Unit tests / Unit tests / Linux (5.10)	4m 32s
Unit tests / Unit tests / Linux (6.0)	5m 3s
Unit tests / Unit tests / Linux (nightly-next)	5m 37s
Unit tests / Unit tests / Linux (nightly-main)	2m 35s
Cxx interop / Cxx interop / Linux (5.9)	2m 26s
Cxx interop / Cxx interop / Linux (5.10)	2m 17s
Cxx interop / Cxx interop / Linux (6.0)	2m 41s
Cxx interop / Cxx interop / Linux (nightly-next)	3m 19s
Cxx interop / Cxx interop / Linux (nightly-main)	2m 31s
	44m 21s

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