fix: ignore qpdf warnings (#2952)

[Abdurrahman-shaikh]

Description of Changes

Please provide a summary of the changes, including:

• What was changed

  • Modified the qpdf command execution by adding the --no-warn flag

• Why the change was made

  • The warning is misleading because the object is still present, so it doesn't indicate a real error. Suppressing it with --no-warn ensures the compression process completes successfully.

• Any challenges encountered

Closes #2952

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Checklist

General

• [x] I have read the Contribution Guidelines
• [x] I have read the Stirling-PDF Developer Guide (if applicable)
• [ ] I have read the How to add new languages to Stirling-PDF (if applicable)
• [x] I have performed a self-review of my own code
• [x] My changes generate no new warnings

Documentation

• [ ] I have updated relevant docs on Stirling-PDF's doc repo (if functionality has heavily changed)
• [ ] I have read the section Add New Translation Tags (for new translation tags only)

UI Changes (if applicable)

• [ ] Screenshots or videos demonstrating the UI changes are attached (e.g., as comments or direct attachments in the PR)

Testing (if applicable)

• [x] I have tested my changes locally. Refer to the Testing Guide for more details.