Add explicit note on empty constructor

See gh-35773

spring-core/src/main/java21/org/springframework/core/task/VirtualThreadDelegate.java

@@ -31,7 +31,7 @@ final class VirtualThreadDelegate {
 	private final Thread.Builder threadBuilder = Thread.ofVirtual();
 
 	public VirtualThreadDelegate() {
-
+		// Matching constructor in dummy version, avoiding jar verification issues.
 	}
 
 	public ThreadFactory virtualThreadFactory() {