sources: prevent deletion of built-in source #27849

Job	Run time
lint (bandit)	1m 45s
lint (black)	1m 48s
test-migrations	2m 18s
lint (codespell)	1m 46s
lint (pending-migrations)	1m 41s
lint (ruff)	1m 30s
test-integration	5m 54s
test-e2e (proxy)	8m 5s
test-migrations-from-stable - PostgreSQL 15-alpine	23m 9s
test-e2e (oauth)	8m 55s
test-migrations-from-stable - PostgreSQL 16-alpine	23m 21s
test-unittest - PostgreSQL 15-alpine	19m 25s
test-e2e (oauth-oidc)	5m 41s
test-unittest - PostgreSQL 16-alpine	18m 58s
test-e2e (saml)	6m 0s
test-e2e (ldap)	10m 6s
test-e2e (radius)	5m 2s
test-e2e (scim)	3m 54s
test-e2e (flows)	4m 36s
ci-core-mark	3s
build	0s
pr-comment	0s
	2h 33m 57s

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