Replace System Rules with System Lambda

System Lambda is more specific. It only wraps the part of the code that
produces the output.

subclass-sandbox/pom.xml

@@ -42,7 +42,7 @@
         </dependency>
         <dependency>
             <groupId>com.github.stefanbirkner</groupId>
-            <artifactId>system-rules</artifactId>
+            <artifactId>system-lambda</artifactId>
         </dependency>
         <dependency>
             <groupId>org.junit.jupiter</groupId>