Fix Checkstyle suppressions DTD link.
diff --git a/src/conf/checkstyle-suppressions.xml b/src/conf/checkstyle-suppressions.xml
index 2494608..e0ef08d 100644
--- a/src/conf/checkstyle-suppressions.xml
+++ b/src/conf/checkstyle-suppressions.xml
@@ -17,8 +17,8 @@
-->
<!DOCTYPE suppressions PUBLIC
- "-//Puppy Crawl//DTD Suppressions 1.1//EN"
- "http://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
+ "-//Checkstyle//DTD SuppressionFilter Configuration 1.0//EN"
+ "https://checkstyle.org/dtds/suppressions_1_0.dtd">
<!-- SEE: http://checkstyle.sourceforge.net/config.html#Examples -->
<suppressions>
<suppress checks="LineLength" files="InstructionFinder.java"/> <!-- TODO later -->
