Trim whitespace in artist names in Spotify.artists

Basically Discord retrieves the data like
`artist1; artist2; artist3` and when you split only by `;` the results
will be: `[artist1, " artist2", " artist3"]`

discord/activity.py

@@ -513,7 +513,7 @@ class Spotify:
     @property
     def artists(self):
         """List[:class:`str`]: The artists of the song being played."""
-        return self._state.split(';')
+        return self._state.split('; ')
 
     @property
     def artist(self):