ci: Remove Linux 5.8 configuration #45

Job	Run time
Integration tests	1m 17s
Soundness / API breakage check	1m 22s
Soundness / Broken symlinks check	4s
Soundness / Documentation check	1m 32s
Soundness / Format check	38s
Soundness / License headers check	4s
Soundness / Python lint check	4s
Soundness / Shell check	44s
Soundness / Unacceptable language check	3s
Swift 6 Language Mode / Swift 6 language mode	1m 17s
Soundness / YAML lint check	3s
Unit tests / Unit tests / Linux (5.9)	25s
Unit tests / Unit tests / Linux (5.10)	28s
Unit tests / Unit tests / Linux (6.0)	1m 22s
Unit tests / Unit tests / Linux (nightly-6.0)	1m 37s
Unit tests / Unit tests / Linux (nightly-main)	2m 11s
	13m 11s

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