Make PAPI expansion persist (#4986)

src/main/java/com/gmail/nossr50/placeholders/PapiExpansion.java

@@ -41,6 +41,11 @@ public class PapiExpansion extends PlaceholderExpansion {
         return "1.0,0";
     }
 
+    @Override
+    public boolean persist() {
+        return true;
+    }
+
     @Override
     public String getRequiredPlugin() {
         return "mcMMO";