Refactor order clause generation using Stream API.

Closes #3611

Author: Seol-JY

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/QueryUtils.java

@@ -292,11 +292,11 @@ public static String applySorting(String query, Sort sort, @Nullable String alia
 		Set<String> selectionAliases = getFunctionAliases(query);
 		selectionAliases.addAll(getFieldAliases(query));
 
-		for (Order order : sort) {
-			builder.append(getOrderClause(joinAliases, selectionAliases, alias, order)).append(", ");
-		}
+		String orderClauses = sort.stream()
+			.map(order -> getOrderClause(joinAliases, selectionAliases, alias, order))
+			.collect(Collectors.joining(", "));
 
-		builder.delete(builder.length() - 2, builder.length());
+		builder.append(orderClauses);
 
 		return builder.toString();
 	}