Cannot copy/paste in the description field of assembly meetings

**Describe the bug**
In the field "description" of the meetings of an assembly the action copy/paste is not allowed. Neither with keyboard nor with mouse.

**Extra data (please complete the following information):**
 - Decidim Version: 0.15.2
 - Decidim installation: https://www.decidimmataro.cat/

**Additional context**
https://meta.decidim.org/processes/bug-report/f/210/proposals/14254

