Kernel: More PID/TID typing

Author: https://github.com/BenWiederhake
Commit: bee08a4b9f
Pull-request: https://github.com/SerenityOS/serenity/pull/3057
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/bgianfo

Kernel/Thread.h

@@ -82,7 +82,7 @@ public:
     explicit Thread(NonnullRefPtr<Process>);
     ~Thread();
 
-    static Thread* from_tid(pid_t);
+    static Thread* from_tid(ThreadID);
     static void finalize_dying_threads();
 
     ThreadID tid() const { return m_tid; }