Fix a strange bug with preserving paragraphs in list items

What does this MR do and why?

Fix a strange bug with preserving paragraphs in list items

When list items are created in RTE, it incorrectly converts some markdown paragraphs to a <p> tag. This commit fixes it.

Changelog

References

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MR acceptance checklist

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How to set up and validate locally

1. Switch to rich text editor.
2. Create a paragraph. Press enter.
3. Create two list items after the paragraph.
4. Switch to plain text editor.

Before:

<p>paragraph</p>

* 
  <p>list item 1</p>

* 
  <p>list item 2</p>

After:

paragraph

* list item 1
* list item 2