chore: remove multipart IO descriptor warning

[ssheng]

What does this PR address?

Using the multi-part IO descriptor shouldn't be resulting in a warning. 😊

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[codecov]

Codecov Report

Merging #2936 (07a07b7) into main (e02fa41) will decrease coverage by 0.26%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2936      +/-   ##
==========================================
- Coverage   70.75%   70.48%   -0.27%     
==========================================
  Files         104      104              
  Lines        9466     9505      +39     
==========================================
+ Hits         6698     6700       +2     
- Misses       2768     2805      +37     

Impacted Files	Coverage Δ
bentoml/_internal/service/service.py	96.70% <ø> (-0.11%)	⬇️
bentoml/_internal/frameworks/mlflow.py	57.54% <0.00%> (-33.50%)	⬇️
bentoml/_internal/configuration/containers.py	78.50% <0.00%> (ø)
bentoml/_internal/yatai_rest_api_client/schemas.py	93.53% <0.00%> (ø)
bentoml/_internal/runner/runner_handle/remote.py	88.54% <0.00%> (+0.36%)	⬆️
bentoml/_internal/log.py	85.96% <0.00%> (+3.50%)	⬆️

[sauyon]

I feel like this warning should probably exist somewhere, though maybe not everywhere this is used.

[ssheng]

I feel like this warning should probably exist somewhere, though maybe not everywhere this is used.

I'm thinking the warning is not very actionable and advise against something we support.

[sauyon]

I think in the majority of cases users probably want to be using JSON output or similar and not multipart.

We should probably have some sort of support for JSONifying multiple IO descriptor outputs; having our default output be a multipart response is very strange in my opinion.