Use a better method name for StoredProfile.isPremium

bungee/src/main/java/com/github/games647/fastlogin/bungee/listener/PluginMessageListener.java

@@ -131,7 +131,7 @@ public class PluginMessageListener implements Listener {
             loginSession.setRegistered(true);
 
             if (!loginSession.isAlreadySaved()) {
-                playerProfile.setPremium(true);
+                playerProfile.setOnlinemodePreferred(true);
                 plugin.getCore().getStorage().save(playerProfile);
                 loginSession.setAlreadySaved(true);
             }

bungee/src/main/java/com/github/games647/fastlogin/bungee/task/AsyncToggleMessage.java

@@ -69,7 +69,7 @@ public class AsyncToggleMessage implements Runnable {
             return;
         }
 
-        playerProfile.setPremium(false);
+        playerProfile.setOnlinemodePreferred(false);
         playerProfile.setId(null);
         core.getStorage().save(playerProfile);
         PremiumToggleReason reason = (!isPlayerSender || !sender.getName().equalsIgnoreCase(playerProfile.getName()))
@@ -86,7 +86,7 @@ public class AsyncToggleMessage implements Runnable {
             return;
         }
 
-        playerProfile.setPremium(true);
+        playerProfile.setOnlinemodePreferred(true);
         core.getStorage().save(playerProfile);
         PremiumToggleReason reason = (!isPlayerSender || !sender.getName().equalsIgnoreCase(playerProfile.getName()))
             ? PremiumToggleReason.COMMAND_OTHER : PremiumToggleReason.COMMAND_SELF;