ci: Add missing environment variable to integration-test #99

Job	Run time
Compatibility test	1m 35s
Swift 6 Language Mode	0s
Example packages / Linux (5.8)	21s
Example packages / Linux (5.9)	1m 26s
Example packages / Linux (5.10)	1m 27s
Integration test / Linux (5.8)	22s
Example packages / Linux (nightly-6.0)	1m 29s
Integration test / Linux (5.9)	1m 27s
Example packages / Linux (nightly-main)	27s
Soundness / API breakage check	1m 27s
Integration test / Linux (5.10)	1m 27s
Integration test / Linux (nightly-6.0)	1m 27s
Integration test / Linux (nightly-main)	26s
Soundness / Broken symlinks check	4s
Soundness / Documentation check	1m 26s
Soundness / Format check	35s
Soundness / License headers check	4s
Soundness / Shell check	30s
Soundness / Unacceptable language check	2s
Unit tests / Unit tests / Linux (5.8)	21s
Unit tests / Unit tests / Linux (5.9)	1m 25s
Unit tests / Unit tests / Linux (5.10)	1m 27s
Unit tests / Unit tests / Linux (nightly-6.0)	1m 25s
Unit tests / Unit tests / Linux (nightly-main)	27s
	21m 7s

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