Set media type correctly in the roon integration- so the media card correctly displays the artist. (#139871)

Set media type correctly - so media card display works properly.

homeassistant/components/roon/media_player.py

@@ -329,6 +329,11 @@ class RoonDevice(MediaPlayerEntity):
         """Album artist of current playing media (Music track only)."""
         return self.media_artist
 
+    @property
+    def media_content_type(self) -> str:
+        """Return the media type."""
+        return MediaType.MUSIC
+
     @property
     def supports_standby(self):
         """Return power state of source controls."""