Rename nightly_6_1 params to nightly_next #278

Job	Run time
Compatibility test	5m 26s
Unit tests / Construct unit test matrix	5s
Example packages / Windows (6.0)	1s
Example packages / Linux (5.9)	23m 43s
Example packages / Windows (nightly-6.1)	3s
Example packages / Linux (5.10)	20m 36s
Example packages / Windows (nightly-main)	2s
Example packages / Linux (6.0)	24m 12s
Example packages / Linux (nightly-6.1)	31m 8s
Example packages / Linux (nightly-main)	35s
Integration test / Linux (5.9)	1m 41s
Integration test / Linux (5.10)	1m 37s
Integration test / Linux (6.0)	1m 53s
Integration test / Linux (nightly-6.1)	2m 15s
Integration test / Linux (nightly-main)	36s
Integration test / Windows (6.0)	3s
Integration test / Windows (nightly-6.1)	2s
Soundness / API breakage check	0s
Integration test / Windows (nightly-main)	2s
Soundness / Broken symlinks check	3s
Soundness / Documentation check	1m 44s
Soundness / Format check	32s
Soundness / License headers check	4s
Soundness / Python lint check	5s
Soundness / Shell check	32s
Soundness / Unacceptable language check	5s
Soundness / YAML lint check	0s
Unit tests / Unit tests / Linux (5.9)	1m 34s
Unit tests / Unit tests / Linux (5.10)	1m 30s
Unit tests / Unit tests / Linux (6.0)	1m 50s
Unit tests / Unit tests / Linux (nightly-next)	2m 57s
Unit tests / Unit tests / Linux (nightly-main)	2m 50s
	2h 7m 46s

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