Promote experimental APIs as stable

- HTML support and Kotlin support no more experimental
- The only left over experimental APIs are java preview features

pmd-kotlin/src/main/java/net/sourceforge/pmd/lang/kotlin/KotlinLanguageModule.java

@@ -4,7 +4,6 @@
 
 package net.sourceforge.pmd.lang.kotlin;
 
-import net.sourceforge.pmd.annotation.Experimental;
 import net.sourceforge.pmd.cpd.CpdLexer;
 import net.sourceforge.pmd.lang.LanguagePropertyBundle;
 import net.sourceforge.pmd.lang.LanguageRegistry;
@@ -13,10 +12,7 @@ import net.sourceforge.pmd.lang.kotlin.cpd.KotlinCpdLexer;
 
 /**
  * Language Module for Kotlin
- *
- * <p>Note: Kotlin support is considered an experimental feature. The AST structure might change.</p>
  */
-@Experimental
 public class KotlinLanguageModule extends SimpleLanguageModuleBase {
     private static final String ID = "kotlin";