fixup! fix fail test run with enabled junit.testFilter option

Review: I think this is a safer way to do it. In the end, the error says "can't remove the root of a hierarchy", so it makes sense to exactly guard against this, and also it then only uses the general JUnit Platform API and doesn't rely on ArchUnit specifics (and `AbstractArchUnitTestDescriptor` is more an implementation detail, it's more by accident that the rule descriptors, etc., inherit from this, but the engine descriptor doesn't).

archunit-junit/junit5/engine/src/main/java/com/tngtech/archunit/junit/internal/ArchUnitSystemPropertyTestFilterJUnit5.java

@@ -40,16 +40,15 @@ void filter(TestDescriptor descriptor) {
 
         String testFilterProperty = configuration.getProperty(JUNIT_TEST_FILTER_PROPERTY_NAME);
         List<String> memberNames = Splitter.on(",").splitToList(testFilterProperty);
-        Predicate<TestDescriptor> shouldRunPredicate =
-            testDescriptor -> !(testDescriptor instanceof AbstractArchUnitTestDescriptor) || memberNameMatches(testDescriptor, memberNames);
+        Predicate<TestDescriptor> shouldRunPredicate = testDescriptor -> memberNameMatches(testDescriptor, memberNames);
         removeNonMatching(descriptor, shouldRunPredicate);
     }
 
     private void removeNonMatching(TestDescriptor descriptor, Predicate<TestDescriptor> shouldRunPredicate) {
         ImmutableSet.copyOf(descriptor.getChildren())
                 .forEach(child -> removeNonMatching(child, shouldRunPredicate));
 
-        if (descriptor.getChildren().isEmpty() && !shouldRunPredicate.test(descriptor)) {
+        if (!descriptor.isRoot() && descriptor.getChildren().isEmpty() && !shouldRunPredicate.test(descriptor)) {
             descriptor.removeFromHierarchy();
         }
     }