Replace a net.minecraft accessor with a public attr.

By: Stéphan Kochen <stephan@kochen.nl>

paper-server/src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -148,7 +148,7 @@ public final class CraftServer implements Server {
     }
 
     public int getMaxPlayers() {
-        return server.getMaxPlayers();
+        return server.e;
     }
 
     public PluginManager getPluginManager() {