NOTE: Must be done before first: {T377186}
## User Story:
As a user I want to be able to remove a favourited template if I do not need it anymore, so that I can keep my favourites list tidy.
## Acceptance criteria:
* Favourite templates show as a solid icon in the search results, and it can be clicked to unfavourite the template.
* Show a bubble notification after removal
* Add undo option to the post-remove notification
* The favourites list has the same unfavourite icon, with the same behaviour (the list item will be removed on unfavouriting)
## Details for QA:
* Favourites are actually removed from the user's preferences
* Undo (in the bubble notification) works and the favourite template is returned, the icon returns to solid and the template returns to the list of all favourites.
## Designs:
https://www.figma.com/design/QWD6oDEz9NMEnF2ppVc4Xq/Template-recall-and-discovery?node-id=765-5322&node-type=canvas&t=yN2wqePQH3we7dMn-0
## Subtasks
* Unfavourite template when clicking the icon in the search results or template list (icon to be added to the latter)
* Add post-removal bubble notification, with undo option
* Deploy template favourites
* Remove feature flag