Audio only mode will be toggleable only from the VideoStatusLabel,
so remove AudioOnlyButton from the toolbar and delete the component
itself. As a result of the button being removed, a truthy check in
VideoStatusLabel was also removed to ensure it will display as it
is now the only way to toggle audio only mode. Also set the cursor
on VideoStatusLabel to always be default, so it can never show the
text cursor.

Audio only mode can be used to save bandwidth. In this mode local video is muted
and last N is set to 0, thus disabling all remote video.

When this mode is enabled avatars are shown.