ci: switch to ubuntu-24.04 image for testing #26166

Job	Run time
lint (bandit)	1m 49s
test-migrations	2m 59s
lint (black)	2m 41s
lint (codespell)	2m 30s
lint (pending-migrations)	1m 56s
test-migrations-from-stable - PostgreSQL 15-alpine	22m 24s
lint (ruff)	1m 53s
test-migrations-from-stable - PostgreSQL 16-alpine	22m 12s
test-unittest - PostgreSQL 15-alpine	19m 19s
test-unittest - PostgreSQL 16-alpine	18m 28s
test-e2e (proxy)	7m 47s
test-integration	6m 3s
test-e2e (oauth)	7m 27s
test-e2e (oauth-oidc)	5m 44s
test-e2e (saml)	6m 19s
test-e2e (ldap)	10m 40s
test-e2e (radius)	5m 19s
test-e2e (scim)	4m 12s
test-e2e (flows)	4m 46s
ci-core-mark	1s
build (amd64)	3m 44s
build (arm64)	27m 1s
pr-comment	3s
	3h 5m 17s

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