Fix VirtualThreadsDebugViewTests (#969)

+ ensure test project TwoThree sets also target to 23.

Author: stephan-herrmann

org.eclipse.jdt.debug.tests/tests/org/eclipse/jdt/debug/tests/AbstractDebugTest.java

@@ -705,6 +705,7 @@ synchronized void assert23Project() {
 				jp = createProject(TWENTYTHREE_PROJECT_NAME, JavaProjectHelper.TEST_23_SRC_DIR.toString(), JavaProjectHelper.JAVA_SE_23_EE_NAME, false);
 				jp.setOption(JavaCore.COMPILER_SOURCE, JavaCore.VERSION_23);
 				jp.setOption(JavaCore.COMPILER_COMPLIANCE, JavaCore.VERSION_23);
+				jp.setOption(JavaCore.COMPILER_CODEGEN_TARGET_PLATFORM, JavaCore.VERSION_23);
 				cfgs.add(createLaunchConfiguration(jp, "Main21"));
 				loaded23 = true;
 				waitForBuild();