Describe the bug
As an admin, when enabling rich text editor for participants, and exporting proposals for example, I find HTML tags in the export.
This makes it hard for teams to analyse proposals exports.

To Reproduce
Steps to reproduce the behavior:

1. Go to a Proposal component with proposals and rich text editor enabled for participants
2. Export those proposals
3. See HTML tags in the export

Expected behavior
As an admin, when enabling rich text editor for participants, I expect exports to be cleaned without HTML tags.

Screenshots

Extra data
Tested on try.decidim.org (0.26.1)

Additional context
#5451