Remove backend_cpu dependency from setup.py

setup.py

@@ -108,7 +108,7 @@ if __name__ == '__main__':
         cmdclass={
             'build_ext': CMakeBuild,
         },
-        install_requires=['aidge_core','aidge_backend_cpu'],
+        install_requires=['aidge_core'],
         zip_safe=False,
 
     )