MdeModulePkg CapsuleApp:Remove two redundant Guids

MdeModulePkg CapsuleApp:Remove two redundant Guids

Remove two redundant Guids which are not used.
They are gEfiCertTypeRsa2048Sha256Guid and
gEfiCertPkcs7Guid.This is an improved version of
https://bugzilla.tianocore.org/show_bug.cgi?id=1062

Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: shenglei <shenglei.zhang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>