Etherpad Popout Button not working

### Description

Etherpad Popout Button not working. Getting "403 Forbidden"

### Steps to reproduce

- Add the Etherpad Widget to a room
- Give the room a custom name (not sure if relevant)
- using hyphens as bullet points
- click popout button

Describe how what happens differs from what you expected.
- browser opens with 403 forbidden error

Logs being sent: no

### Version information

- **Platform**: desktop app
- **Version**: Element version: 1.7.3, olm version: 3.1.3
- **OS**: win x64
- **Browser** (after clicking popout button): Firefox, also tested the given URL in chromium. Same error

The popout Button tries to open a URL like this:

https://scalar.vector.im/api/widgets/etherpad.html?padName=!HltKLmaRClmCrnRPXt:matrix.org_mypad&userName=%40some_username%3Amatrix.org

(pad ID and user ID changed)

But I think, it should send this URL to the Browser instead:

https://scalar.vector.im/etherpad/p/!HltKLmaRClmCrnRPXt:matrix.org_mypad?userName=%40some_username%3Amatrix.org

Because that actually works.