Fix Checkstyle suppressions DTD link.
diff --git a/core/checkstyle-suppressions.xml b/core/checkstyle-suppressions.xml
index 469b82a..d385aaf 100644
--- a/core/checkstyle-suppressions.xml
+++ b/core/checkstyle-suppressions.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE suppressions PUBLIC
-     "-//Puppy Crawl//DTD Suppressions 1.0//EN"
+     -//Checkstyle//DTD SuppressionFilter Configuration 1.0//EN
      "https://checkstyle.org/dtds/suppressions_1_0.dtd">
 <!--
    Licensed to the Apache Software Foundation (ASF) under one or more