kernel: Remove unnecessary includes

Removes unnecessary direct dependencies in some headers and also gets
rid of indirect dependencies that were being relied on to be included.

src/core/hle/kernel/server_session.h

@@ -6,12 +6,12 @@
 
 #include <memory>
 #include <string>
-#include "common/assert.h"
+#include <vector>
+
 #include "common/common_types.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/wait_object.h"
 #include "core/hle/result.h"
-#include "core/memory.h"
 
 namespace Kernel {