Fix broken test of const repeated field iterators
Fix broken test of const repeated field iterators

The old version had a NOP for loop, which doesn't make sense. I'm pretty
sure this was the original intention. Newer GCC's
-Wunused-but-set-variable flags the old version.

google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf