Fix fresnel sampling

Wrong factor 1/2 in code, due to assumed padding in reference paper.

src/hotopy/holo/propagation.py

@@ -286,7 +286,7 @@ class FresnelTFPropagator(FourierConvolutionPropagator):
     def _init_kernel(self):
         # verify sufficient padding
         if not check_fresnelTF_sampling(self._pad_shape, self._fresnel_numbers):
-            n_min = get_fresnel_critical_sampling(self._pad_shape, self._fresnel_numbers)
+            n_min = get_fresnel_critical_sampling(self._fresnel_numbers)
             logger.warning(
                 UserWarning(
                     f"{self.__class__.__name__}: "