[#70419] Fix usages of `Blankslate` description slot

[myabc]

Ticket

https://community.openproject.org/wp/70419

What are you trying to accomplish?

Fixes generated HTML

Content passed to #with_description must not include HTML block elements (such as flex layouts). Blankslate always renders descriptions within a p element, which may only contain inline HTML elements.

FYI @opf/sirius

Screenshots

In most cases, the appearance should be virtually unchanged. However in the case of the Meetings template page, making the secondary action actionable requires cutting down the text (thereby following these guidelines).

Before

After

Merge checklist

• [ ] Added/updated tests
• [ ] Added/updated documentation in Lookbook (patterns, previews, etc)
• [ ] Tested major browsers (Chrome, Firefox, Edge, ...)