1. Change default PCD in SecurityPkg to 4 (DENY_EXECUTE) in DEC file.

1. Change default PCD in SecurityPkg to 4 (DENY_EXECUTE) in DEC file.
2. ASSERT if PCD value is set to 5 (QUERY_USER_ON_SECURITY_VIOLATION).
3. Update override PCD setting from 5 to 4 in platform DSC file.
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Ni Ruiyu <ruiyu.ni@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14607 6f19259b-4bc3-4df7-8a09-765794883524