migration: Use error_propagate() in migrate_error_propagate()

It improves readability, as suggested by Markus.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/20251202175317.1186544-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
1 file changed