Polishing.

Co-authored-by: Peter-Josef Meisch <[email protected]>

Author: youssef3wi

src/main/java/org/springframework/data/elasticsearch/core/mapping/CreateIndexSettings.java

@@ -69,7 +69,7 @@ public Document getMapping() {
 
     public static class Builder {
         private IndexCoordinates indexCoordinates;
-        private Set<Alias> aliases = new HashSet<>();
+        private final Set<Alias> aliases = new HashSet<>();
 
         private Map<String, Object> settings;