Everywhere: Use a forward declaration for pointers to Threading::Thread

Author: https://github.com/Zaggy1024
Commit: 2aaf53bd2c
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6223
Reviewed-by: https://github.com/konradekk

Libraries/LibWeb/HTML/RenderingThread.cpp

@@ -5,6 +5,7 @@
  */
 
 #include <LibCore/EventLoop.h>
+#include <LibThreading/Thread.h>
 #include <LibWeb/HTML/RenderingThread.h>
 #include <LibWeb/HTML/TraversableNavigable.h>
 #include <LibWeb/Painting/DisplayListPlayerSkia.h>

Libraries/LibWeb/HTML/RenderingThread.h

@@ -10,8 +10,8 @@
 #include <AK/Queue.h>
 #include <LibCore/Promise.h>
 #include <LibThreading/ConditionVariable.h>
+#include <LibThreading/Forward.h>
 #include <LibThreading/Mutex.h>
-#include <LibThreading/Thread.h>
 #include <LibWeb/Forward.h>
 #include <LibWeb/Page/Page.h>