chore: Remove redundant text message for file input in OpenAIPrompt

[levscaut]

Related Issues/PRs

#xxx

What changes are proposed in this pull request?

When using file input in OpenAIPrompt before, a text message will be sent along: The name of the file to analyze is %s.\nHere is the content:\n, this will cause info leak in file name, as long as extra token used. So it's for the best to remove this piece of message.

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.

[github-actions]

Hey @levscaut 👋!
Thank you so much for contributing to our repository 🙌.
Someone from SynapseML Team will be reviewing this pull request soon.

We use semantic commit messages to streamline the release process.
Before your pull request can be merged, you should make sure your first commit and PR title start with a semantic prefix.
This helps us to create release messages and credit you for your hard work!

Examples of commit messages with semantic prefixes:

• fix: Fix LightGBM crashes with empty partitions
• feat: Make HTTP on Spark back-offs configurable
• docs: Update Spark Serving usage
• build: Add codecov support
• perf: improve LightGBM memory usage
• refactor: make python code generation rely on classes
• style: Remove nulls from CNTKModel
• test: Add test coverage for CNTKModel

To test your commit locally, please follow our guild on building from source.
Check out the developer guide for additional guidance on testing your change.

[ranadeepsingh]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull request overview

This PR removes a redundant text message that was previously sent along with file inputs in the OpenAIPrompt class. The removed message contained the filename and an introductory text, which could leak sensitive information and unnecessarily consume tokens. The change simplifies the file attachment logic by directly including the file content without the wrapper message.

• Removed the multiModalTextPrompt constant and its usage
• Modified wrapFileToMessagesList to return only the file message content
• Eliminates potential filename information leakage and reduces token consumption

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.07%. Comparing base (38b53c6) to head (79a9540).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2448      +/-   ##
==========================================
- Coverage   84.38%   83.07%   -1.31%     
==========================================
  Files         335      335              
  Lines       17690    17688       -2     
  Branches     1619     1610       -9     
==========================================
- Hits        14928    14695     -233     
- Misses       2762     2993     +231     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.