Common: Cleanup key_map includes.

src/core/hle/kernel/kernel.h

@@ -4,10 +4,11 @@
 
 #pragma once
 
-#include <boost/intrusive_ptr.hpp>
+#include <boost/smart_ptr/intrusive_ptr.hpp>
 
+#include <algorithm>
 #include <array>
-#include <memory>
+#include <cstddef>
 #include <string>
 #include <vector>
 
@@ -16,8 +17,6 @@
 #include "core/hle/hle.h"
 #include "core/hle/result.h"
 
-struct ApplicationInfo;
-
 namespace Kernel {
 
 class Thread;