robots.txt: disallow indexing of /error/403 page.

Correction for 839b331 commit.

Author: php-coder

src/main/java/ru/mystamps/web/controller/RobotsTxtController.java

@@ -53,6 +53,7 @@ public void getRobotsText(HttpServletResponse response) {
 			writer.println("Disallow: " + Url.ADD_SERIES_PAGE);
 			writer.println("Disallow: " + Url.ADD_CATEGORY_PAGE);
 			writer.println("Disallow: " + Url.UNAUTHORIZED_PAGE);
+			writer.println("Disallow: " + Url.FORBIDDEN_PAGE);
 			writer.println("Disallow: " + Url.NOT_FOUND_PAGE);
 			writer.println("Disallow: " + Url.INTERNAL_ERROR_PAGE);
 			writer.println("Sitemap: " + Url.PUBLIC_URL + Url.SITEMAP_XML);