Consider a case where the donor failover happens after the donor state doc is marked as garbage collectable but before resolving _forgetMigrationDurablePromise as ok. This would result, in new primary to go into this code path, resulting in new primary to resolve the _forgetMigrationDurablePromise only after the state doc is deleted rather than after marking state doc as garbage collectable, causing donorForgetMigration to wait for a long time (the garbage collection delay) before returning.