Misleading text on empty Pinned messages banner

### Steps to reproduce

1. Open a pinned messages ~~banner~~ panel in a room where the list is empty and you have no right to pin messeges

### Outcome

#### What did you expect?

To see something like "There are no pinned messages. You have no right to pin messages because..."

#### What happened instead?

The text is a bit misleading:
"Pin important messages so that they can be easily discovered
Select a message and choose “Pin” to it include here."

### Application version

Element nightly 2024102001

Start by reproducing the empty pinned-messages panel in an Element room where you cannot pin messages, then locate the displayed empty-state text in the frontend. Update the wording to explain that there are no pinned messages and that the user lacks permission to pin them, then verify the result in the same scenario.

Written by the indexing model from the issue text.