Homeserver list should be scrollable

### Your use case

#### What would you like to do?

Homeserver list in public room search dialogue > server chooser should be scrollable

#### Why would you like to do it?

If there are too many homeservers in the list, the top extends beyond the view and it is not possible to select it

#### How would you like to achieve it?

Make the list scrollable

### Have you considered any alternatives?

None

### Additional context

The first server matrix.org is hidden from view and it is not possible to select it:

1920x1080 px resolution


Reproduce the public room search dialogue at the server chooser with enough homeservers to exceed the viewport, using the reported 1920x1080 context. Inspect that chooser's layout and make the list scrollable so the first server, matrix.org, remains selectable; verify the behavior with a long list.

Written by the indexing model from the issue text.