🚨 fftpack: fix stubtest error on numpy<2 (#786)

Author: jorenham

scipy-stubs/fftpack/helper.pyi

@@ -2,12 +2,12 @@
 from typing import Final
 from typing_extensions import deprecated
 
+from numpy.fft import fftfreq
+
 __all__ = ["fftfreq", "fftshift", "ifftshift", "next_fast_len", "rfftfreq"]
 
 __MESSAGE: Final = "will be removed in SciPy v2.0.0"
 
-@deprecated(__MESSAGE)
-def fftfreq(n: object, d: object = ..., device: object = ...) -> object: ...
 @deprecated(__MESSAGE)
 def fftshift(x: object, axes: object = ...) -> object: ...
 @deprecated(__MESSAGE)