Remove aidge_backend_cpu dependency from CMakeLists.txt

CMakeLists.txt

@@ -31,7 +31,6 @@ endif()
 ##############################################
 # Find system dependencies
 find_package(aidge_core REQUIRED)
-find_package(aidge_backend_cpu REQUIRED)
 find_package(OpenCV REQUIRED)
 if (${OpenCV_VERSION_MAJOR} LESS 3)
     MESSAGE(FATAL_ERROR "Unsupported OpenCV version. OpenCV 3.0.0+ is required")
@@ -47,7 +46,6 @@ add_library(${module_name} ${src_files} ${inc_files})
 target_link_libraries(${module_name}
     PUBLIC
         _aidge_core # _ is added because we link the target not the project
-        _aidge_backend_cpu
 )
 
 target_link_libraries(${module_name} PUBLIC ${OpenCV_LIBS})