message: [XLA] Shorten "custom_call_target" to "target" in XLA graph dumper.
  Make CustomCall nodes a bit smaller by shortening
  "custom_call_target=" to "target=".
diff: @@ -1056,7 +1056,7 @@ string HloDotDumper::GetInstructionNodeExtraInfo(const HloInstruction* instr) {
  case HloOpcode::kBatchNormGrad:
  return Printf("feature_index=%lld", instr->feature_index());
  case HloOpcode::kCustomCall:
  - return Printf("custom_call_target=%s", instr->custom_call_target());
  + return Printf("target=%s", instr->custom_call_target());
  case HloOpcode::kSlice:
  return std::all_of(instr->slice_strides().begin(),
  instr->slice_strides().end(),
  