Bump com.puppycrawl.tools:checkstyle from 10.20.2 to 10.21.1 (#167)

Author: dependabot[bot]

pom.xml

@@ -265,7 +265,7 @@
                     <dependency>
                         <groupId>com.puppycrawl.tools</groupId>
                         <artifactId>checkstyle</artifactId>
-                        <version>10.20.2</version>
+                        <version>10.21.1</version>
                     </dependency>
                 </dependencies>
                 <executions>