adding archunit test for threadgroup

Author: larrydiamond

src/test/java/com/ldiamond/sqgraph/ArchitectureUnitTests.java

@@ -31,6 +31,9 @@ public class ArchitectureUnitTests {
     @ArchTest
     static final ArchRule no_treeset = noClasses().should().callConstructor(java.util.TreeSet.class).because("Use ConcurrentSkipListSet");
 
+    @ArchTest
+    static final ArchRule no_threadgroup = noClasses().should().callConstructor(java.lang.ThreadGroup.class).because("Use ExecutorService");
+
     @ArchTest
     static final ArchRule no_treemap = noClasses().should().callConstructor(java.util.TreeMap.class).because("Use ConcurrentSkipListMap");