CI: switch away from buildjet runners temporarily #5786

Job	Run time
Build test artifacts (postgres)	56m 16s
Build test artifacts (sqlite)	55m 55s
Build test binaries	25m 54s
demo-native	2m 47s
test-sqlite (1)	3m 46s
test-sqlite (2)	3m 45s
test-sqlite (3)	4m 13s
test-sqlite (4)	2m 11s
test-sqlite (5)	4m 12s
test-sqlite (6)	1m 31s
test-sqlite (7)	4m 50s
test-sqlite (8)	2m 33s
test-sqlite (9)	2m 16s
test-sqlite (10)	2m 43s
test-postgres (1)	2m 29s
test-postgres (2)	4m 5s
test-integration (2)	11m 33s
test-postgres (3)	3m 53s
test-integration (99)	4m 13s
test-postgres (4)	1m 59s
test-postgres (5)	4m 3s
test-postgres (6)	3m 44s
test-postgres (7)	4m 45s
test-postgres (8)	2m 3s
test-postgres (9)	2m 23s
test-postgres (10)	2m 56s
	3h 40m 58s

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