Fix typo in repeated field generation.
Fix typo in repeated field generation.

alexeyxo/protobuf-objc,E-B-Smith/protobuf-objc,E-B-Smith/protobuf-objc,alexeyxo/protobuf-objc,E-B-Smith/protobuf-objc,alexeyxo/protobuf-objc,alexeyxo/protobuf-objc,E-B-Smith/protobuf-objc