Do not hardcode release in VirtualThreadTest

As the test skips compilation of the code only when run on Java 19+
there is no need to hardcode release but rather let the JVM use it's
default.
Skip getting and passing default DiagnosticCollector as the compiler
will do that when passed null.

org.eclipse.jdt.debug.jdi.tests/tests/org/eclipse/debug/jdi/tests/VirtualThreadTest.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2022 Microsoft Corporation and others.
+ * Copyright (c) 2022, 2024 Microsoft Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -23,7 +23,6 @@
 import java.util.List;
 import java.util.Locale;
 
-import javax.tools.DiagnosticCollector;
 import javax.tools.JavaCompiler;
 import javax.tools.JavaCompiler.CompilationTask;
 import javax.tools.JavaFileObject;
@@ -112,16 +111,15 @@ protected static void compileTestProgram() throws Exception {
 	}
 
 	private static void compileFiles(String sourceFilePath, String outputPath) throws Exception {
-		DiagnosticCollector<? super JavaFileObject> diagnosticCollector = new DiagnosticCollector<>();
-		StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnosticCollector, Locale.ENGLISH, StandardCharsets.UTF_8);
+		StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, Locale.ENGLISH, StandardCharsets.UTF_8);
 		Iterable<? extends JavaFileObject> javaFileObjects = fileManager.getJavaFileObjects(new File(sourceFilePath));
 		File outputFolder = new File(outputPath);
 		if (!outputFolder.exists()) {
 			Files.createDirectories(outputFolder.toPath());
 		}
-		List<String> options = List.of("--release", "21", "-d", outputFolder.getAbsolutePath(), "-g", "-proc:none");
+		List<String> options = List.of("-d", outputFolder.getAbsolutePath(), "-g", "-proc:none");
 		final StringWriter output = new StringWriter();
-		CompilationTask task = compiler.getTask(output, fileManager, diagnosticCollector, options, null, javaFileObjects);
+		CompilationTask task = compiler.getTask(output, fileManager, null, options, null, javaFileObjects);
 		boolean result = task.call();
 		if (!result) {
 			throw new IllegalArgumentException("Compilation failed:\n'" + output + "', compiler name: '" + compiler.name()