KabylakeSiliconPkg/SiPkg.dec: Remove Legacy8259 protocol GUID

For modules consumed by platforms within KabylakeOpenBoardPkg &
ClevoOpenBoardPkg, none of them has the dependency on the Legacy8259
protocol. Thus, this commit will remove the duplicated Legacy8259 protocol
GUID within file SiPkg.dec.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Michael Kubacki <michael.a.kubacki@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>