UefiCpuPkg/SmmCpuFeaturesLib: drop obsolete API implementation

UefiCpuPkg/SmmCpuFeaturesLib: drop obsolete API implementation

Commit 0426115b6738 ("UefiCpuPkg: Remove unused API in
SmmCpuFeaturesLib.h", 2022-12-21) removed the declaration of the function
SmmCpuFeaturesAllocatePageTableMemory() from the "SmmCpuFeaturesLib.h"
library class header.

Remove the API's (null-)implementation from UefiCpuPkg/SmmCpuFeaturesLib
as well.

Build-tested with:

  build -a IA32 -a X64 -b NOOPT -p UefiCpuPkg/UefiCpuPkg.dsc -t GCC5

Cc: Eric Dong <eric.dong@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4235
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Dun Tan <dun.tan@intel.com>