TrigT1Interfaces: cmake fixes

Remove unused dependencies.

Trigger/TrigT1/TrigT1Interfaces/CMakeLists.txt

-# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
 
 # Declare the package name:
 atlas_subdir( TrigT1Interfaces )
 
 # External dependencies:
-find_package( XercesC )
 find_package( tdaq-common COMPONENTS CTPfragment )
 
 # Component(s) in the package:
 atlas_add_library( TrigT1Interfaces
                    src/*.cxx
                    PUBLIC_HEADERS TrigT1Interfaces
-                   INCLUDE_DIRS ${XERCESC_INCLUDE_DIRS} ${TDAQ-COMMON_INCLUDE_DIRS}
-                   LINK_LIBRARIES ${TDAQ-COMMON_LIBRARIES} ${XERCESC_LIBRARIES} AthContainers AthenaBaseComps AthenaKernel GaudiKernel TrigT1MuctpiBits TrigConfData
+                   INCLUDE_DIRS ${TDAQ-COMMON_INCLUDE_DIRS}
+                   LINK_LIBRARIES ${TDAQ-COMMON_LIBRARIES} AthContainers AthenaBaseComps AthenaKernel GaudiKernel TrigConfData
                    PRIVATE_LINK_LIBRARIES TrigConfL1Data)
 
 atlas_add_dictionary( TrigT1InterfacesDict