[BUG] Running the nlp_si_detection example pipeline prints a warning about a slow edge

[dagardner-nv]

Describe the bug
The nlp_si_detection pipeline example prints the following warning message about a slow edge. The culprit appears to be the SerializeStage

W20220623 15:41:12.778241 2000453 node.hpp:271] WARNING: A slow edge connection between C++ nodes '[with T = std::shared_ptr<morpheus::MultiResponseProbsMessage>]' and '[with T = std::shared_ptr<morpheus::MultiMessage>]' has been detected. Performance between these nodes can be improved by registering an EdgeConverter at compile time. Without this, conversion to an intermediate python type will be necessary (i.e. C++ -> Python -> C++).

Steps/Code to reproduce bug

morpheus --log_level=DEBUG \
   `# Run a pipeline with 8 threads and a model batch size of 32 (Must match Triton config)` \
   run --num_threads=8 --pipeline_batch_size=1024 --model_max_batch_size=32 \
   `# Specify a NLP pipeline with 256 sequence length (Must match Triton config)` \
   pipeline-nlp --model_seq_length=256 \
   `# 1st Stage: Read from file` \
   from-file --filename=$MORPHEUS_ROOT/examples/data/pcap_dump.jsonlines \
   `# 2nd Stage: Deserialize from JSON strings to objects` \
   deserialize \
   `# 3rd Stage: Preprocessing converts the input data into BERT tokens` \
   preprocess --vocab_hash_file=$MORPHEUS_ROOT/morpheus/data/bert-base-uncased-hash.txt --do_lower_case=True --truncation=True \
   `# 4th Stage: Send messages to Triton for inference. Specify the model loaded in Setup` \
   inf-triton --model_name=sid-minibert-onnx --server_url=localhost:8000 --force_convert_inputs=True \
   `# 5th Stage: Monitor stage prints throughput information to the console` \
   monitor --description "Inference Rate" --smoothing=0.001 --unit inf \
   `# 6th Stage: Add results from inference to the messages` \
   add-class \
   `# 7th Stage: Filtering removes any messages that did not detect SI` \
   filter \
   `# 8th Stage: Convert from objects back into strings` \
   serialize --exclude '^_ts_' \
   `# 9th Stage: A second Monitor stage to monitor the back-half of the pipeline` \
   monitor --description "Serialize Rate" --smoothing=0.001 \
   `# 10th Stage: Write out the JSON lines to the detections.jsonlines file` \
   to-file --filename=detections.jsonlines --overwrite

Expected behavior
No warnings

Environment overview (please complete the following information)

• Environment location: Bare-metal
• Method of Morpheus install: from source