message: [xla] fix Python client bug in AllToAll
diff: @@ -498,7 +498,8 @@ LocalOp ComputationBuilder::Collapse(const LocalOp& operand,
  LocalOp ComputationBuilder::AllToAll(
  const LocalOp& operand, int64 split_dimension, int64 concat_dimension,
  int64 split_count, absl::Span<const ReplicaGroup> replica_groups) {
  - std::vector<ReplicaGroup> rg(replica_groups.size());
  + std::vector<ReplicaGroup> rg;
  + rg.reserve(replica_groups.size());
  for (int i = 0; i < replica_groups.size(); ++i) {
  rg.push_back(replica_groups[i]);
  }
  