fix: retrieve raw content from TinyMCE editor (#31212)

[asadali145]

Description

This backports #31212 to fix https://discuss.openedx.org/t/text-component-does-not-remove-text-with-link-or-insert-a-link-to-text/9029/5 and https://github.mit.edu/xpro/xpro-issues/issues/338.

During the upgrade to TinyMCE v5, we changed the content format to text. However, it ignores changes in HTML tags. This reverts the format to raw.

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[asadali145]

Failing tests are not related to this PR. Tests are fixed in master under #31488. I have added a comment for backport to Olive. Checks should pass after that.

[arslanashraf7]

Looks good 👍 . Tested this locally with olive and it works too. The styling, hyperlinks, and text changes all worked for me.

Someone from the open edX team would need to approve and merge this. As for the failing tests i think we can rebase once the fix PR for that is backported as per your comment above. (Oh, this is already done)

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