Fix Checkstyle suppressions DTD link.
diff --git a/src/site/resources/checkstyle/checkstyle-suppressions.xml b/src/site/resources/checkstyle/checkstyle-suppressions.xml
index e4746a5..275e5c1 100644
--- a/src/site/resources/checkstyle/checkstyle-suppressions.xml
+++ b/src/site/resources/checkstyle/checkstyle-suppressions.xml
@@ -15,7 +15,7 @@
See the License for the specific language governing permissions and
limitations under the License.
-->
-<!DOCTYPE suppressions PUBLIC "-//Puppy Crawl//DTD Suppressions 1.1//EN" "http://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
+<!DOCTYPE suppressions PUBLIC "-//Checkstyle//DTD SuppressionFilter Configuration 1.0//EN" "https://checkstyle.org/dtds/suppressions_1_0.dtd">
<suppressions>
<suppress checks="JavadocMethod" files=".*[/\\]test[/\\].*"/>
<suppress checks="JavadocPackage" files=".*[/\\]test[/\\].*"/>
