chore: OpenAIDefaults bug fixes

[sss04]

Related Issues/PRs

Small bug fixes for OpenAIDefaults.

What changes are proposed in this pull request?

Briefly describe the changes included in this Pull Request.

How is this patch tested?

• I have written tests (not required for typo or doc fix) and confirmed the proposed feature/bug-fix/change works.

Does this PR change any dependencies?

• No. You can skip this section.
• Yes. Make sure the dependencies are resolved correctly, and list changes here.

Does this PR add a new feature? If so, have you added samples on website?

• No. You can skip this section.
• Yes. Make sure you have added samples following below steps.

1. Find the corresponding markdown file for your new feature in website/docs/documentation folder.
   Make sure you choose the correct class estimators/transformers and namespace.
2. Follow the pattern in markdown file and add another section for your new API, including pyspark, scala (and .NET potentially) samples.
3. Make sure the DocTable points to correct API link.
4. Navigate to website folder, and run yarn run start to make sure the website renders correctly.
5. Don't forget to add <!--pytest-codeblocks:cont--> before each python code blocks to enable auto-tests for python samples.
6. Make sure the WebsiteSamplesTests job pass in the pipeline.

[sss04]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.

Project coverage is 12.91%. Comparing base (3ec2ccd) to head (0e7f041).

Files with missing lines	Patch %	Lines
...soft/azure/synapse/ml/services/openai/OpenAI.scala	0.00%	13 Missing ⚠️
...zure/synapse/ml/services/openai/OpenAIPrompt.scala	0.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (3ec2ccd) and HEAD (0e7f041). Click for more details.

HEAD has 142 uploads less than BASE

Flag	BASE (3ec2ccd)	HEAD (0e7f041)
	148	6

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2332       +/-   ##
===========================================
- Coverage   84.52%   12.91%   -71.62%     
===========================================
  Files         328      328               
  Lines       16844    16843        -1     
  Branches     1512     1513        +1     
===========================================
- Hits        14238     2175    -12063     
- Misses       2606    14668    +12062     

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