Make connected pattern paper-only. (#6573)

* Make connected pattern paper-only.

* Add required papermc for connected.

src/main/java/ch/njol/skript/conditions/CondIsOnline.java

@@ -18,13 +18,15 @@
  */
 package ch.njol.skript.conditions;
 
+import ch.njol.skript.Skript;
 import org.bukkit.OfflinePlayer;
 
 import ch.njol.skript.conditions.base.PropertyCondition;
 import ch.njol.skript.doc.Description;
 import ch.njol.skript.doc.Examples;
 import ch.njol.skript.doc.Name;
 import ch.njol.skript.doc.Since;
+import ch.njol.skript.doc.RequiredPlugins;
 import ch.njol.skript.lang.Expression;
 import ch.njol.skript.lang.SkriptParser.ParseResult;
 import ch.njol.util.Kleenean;
@@ -45,10 +47,14 @@
 	    "\twait 1 tick"
 })
 @Since("1.4")
+@RequiredPlugins("Paper 1.20+ (Connected)")
 public class CondIsOnline extends PropertyCondition<OfflinePlayer> {
 
 	static {
-		register(CondIsOnline.class, "(online|:offline|:connected)", "offlineplayers");
+		if (Skript.methodExists(OfflinePlayer.class, "isConnected"))
+			register(CondIsOnline.class, "(online|:offline|:connected)", "offlineplayers");
+		else
+			register(CondIsOnline.class, "(online|:offline)", "offlineplayers");
 	}
 
 	private boolean connected; // https://github.com/SkriptLang/Skript/issues/6100