fix(mlx-swift): remove non-existent cuda.cpp from Package.swift exclude list

cuda.cpp was removed from mlx upstream (refactored into cuda.h) but the
exclude entry was never updated, causing 'Invalid Exclude: File not found'
warning in both xcodebuild and Xcode IDE on every build.

Author: solderzzc

LocalPackages/mlx-swift/Package.swift

@@ -154,7 +154,6 @@ let cmlx = Target.target(
         "mlx/mlx/backend/cuda/compiled.cpp",
         "mlx/mlx/backend/cuda/conv.cpp",
         "mlx/mlx/backend/cuda/cublas_utils.cpp",
-        "mlx/mlx/backend/cuda/cuda.cpp",
         "mlx/mlx/backend/cuda/cudnn_utils.cpp",
         "mlx/mlx/backend/cuda/custom_kernel.cpp",
         "mlx/mlx/backend/cuda/delayload.cpp",