8254627: Cleanup {Abstract,Single,Split}IndexWriter classes

Reviewed-by: hannesw

Author: jonathan-gibbons

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/AbstractIndexWriter.java

@@ -171,11 +171,7 @@ protected void generateOtherFiles(DocletEnvironment docEnv, ClassTree classtree)
         if (options.createIndex()) {
             SystemPropertiesWriter.generate(configuration);
             configuration.mainIndex.addElements();
-            if (options.splitIndex()) {
-                SplitIndexWriter.generate(configuration);
-            } else {
-                SingleIndexWriter.generate(configuration);
-            }
+            IndexWriter.generate(configuration);
             IndexBuilder allClassesIndex = new IndexBuilder(configuration, nodeprecated, true);
             allClassesIndex.addElements();
             AllClassesIndexWriter.generate(configuration, allClassesIndex);