restore final for renamedFiles

Author: Vladimir Kotal

opengrok-indexer/src/main/java/org/opengrok/indexer/history/History.java

@@ -41,7 +41,7 @@ public class History {
      * SCMs) during cache creation.
      * These are relative to repository root.
      */
-    private Set<String> renamedFiles;
+    private final Set<String> renamedFiles;
 
     public History() {
         this(new ArrayList<>());