Fix bug showing duplicate albums

Albums with tracks tagged with different years were showing one instance
of the album for each year present in the tracks. This should fix that.

Persephone/MPDClient/Models/MPDAlbum.swift

@@ -17,8 +17,7 @@ extension MPDClient {
 
     static func == (lhs: MPDAlbum, rhs: MPDAlbum) -> Bool {
       return lhs.title == rhs.title &&
-        lhs.artist == rhs.artist &&
-        lhs.date == rhs.date
+        lhs.artist == rhs.artist
     }
   }
 }