[Pal/Linux-SGX] pal-sgx-sign: Remove unnecessary copy of manifest

Previously, there was a copy of the input (template) manifest to an output
(final SGX) manifest. This copy is unnecessary since the file is overwritten
later anyway. This commit removes this copy and also the shutil import.

Pal/src/host/Linux-SGX/signer/pal-sgx-sign

@@ -4,7 +4,6 @@ import argparse
 import datetime
 import hashlib
 import os
-import shutil
 import struct
 import subprocess
 import sys
@@ -851,8 +850,6 @@ def main_sign(args):
             enclave_heap_min = 0
             manifest['sgx.static_address'] = '0'
 
-    # Add manifest at the top
-    shutil.copy2(args['manifest'], args['output'])
     output_manifest(args['output'], manifest, manifest_layout)
 
     memory_areas = [