Logger should have a virtual destructor

https://bugs.webkit.org/show_bug.cgi?id=274432

Reviewed by David Kilzer and Chris Dumez.

Added the virtual destructor since AggregateLogger subclasses Logger
and has non-POD member variables.

* Source/WTF/wtf/Logger.h:
(WTF::Logger::~Logger):

Canonical link: https://commits.webkit.org/279033@main

Source/WTF/wtf/Logger.h

@@ -126,6 +126,7 @@ WTF_EXPORT_PRIVATE extern Lock loggerObserverLock;
 class Logger : public ThreadSafeRefCounted<Logger> {
     WTF_MAKE_NONCOPYABLE(Logger);
 public:
+    virtual ~Logger() { }
 
     class Observer {
     public: