Add missing copied tests to default sourceset outputdir (#69381)

For all projects that use copied YAML tests AND use the
default sourceset (test) the YAML tests are no longer on
the test class path.

This commit adds them back to the classpath after the
refactoring on #68943

buildSrc/src/main/java/org/elasticsearch/gradle/test/rest/RestResourcesPlugin.java

@@ -156,5 +156,6 @@ public class RestResourcesPlugin implements Plugin<Project> {
             });
 
         defaultSourceSet.getOutput().dir(copyRestYamlApiTask.map(CopyRestApiTask::getOutputResourceDir));
+        defaultSourceSet.getOutput().dir(copyRestYamlTestTask.map(CopyRestTestsTask::getOutputResourceDir));
     }
 }