[WIN32K] Remove incorrect packing specification around _TL, _WIN32THREAD and _THREADINFO structures.

CORE-18140

This was introduced historically in commit 583de66b3 (r7460) to
workaround some compiler problems (or replace already existing
GCC-specific __attribute__((packed)) annotations); however these
structures are in-memory-only, do not describe any on-disk data
format and don't describe hardware-specific data. So they should
have the "natural" alignment of the target platform.

They also have to match the documented layouts at:
https://reactos.org/wiki/Techwiki:Win32k/THREADINFO
https://www.geoffchappell.com/studies/windows/km/win32k/structs/threadinfo/index.htm
at least for the compatible parts that ReactOS shares.

win32ss/user/ntuser/win32.h

@@ -53,7 +53,6 @@ extern HANDLE hModuleWin;    // This Win32k Instance.
 extern struct _CLS *SystemClassList;
 extern BOOL RegisteredSysClasses;
 
-#include <pshpack1.h>
 // FIXME: Move to ntuser.h
 typedef struct _TL
 {
@@ -164,8 +163,6 @@ typedef struct _THREADINFO
 #endif // __cplusplus
 } THREADINFO;
 
-#include <poppack.h>
-
 
 #define IntReferenceThreadInfo(pti) \
     InterlockedIncrement(&(pti)->RefCount)