[QTI] Cannot publish a channel because of an exercise containing strikethrough formatted text

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Observed behavior

Similarly to https://github.com/learningequality/studio/issues/5895 it's not possible to publish the following test channel containing an exercise with a question containing strikethrough formatting of the text: <s>test</>. This issue is not happening on production. No errors in the browser console:

https://github.com/user-attachments/assets/41f29b34-afeb-4abc-a75f-9af73f45a41c

Expected behavior

Formatted text should not impact the publishing of a channel.

Steps to reproduce the issue

1. Sign in to Studio at unstable
2. Go to Channel > Channel editor > New exercise
3. Create an exercise containing strikethrough formatting of the text
4. Attempt to publish the channel

Usage Details

• Studio Unstable
• OS: Windows 11
• Browser: Chrome, Firefox