Change parent of ATOM_SITE_FOURIER_WAVE_VECTOR to MAGNETIC.

Since the CIF_MS dictionary is imported in full (head-in-head import),
all top level categories from the CIF_MS dictionary become automatically
reparented from MS_GROUP to MAGNETIC. Furthermore, the MS_GROUP head category
is not imported at all, thus resulting in a missing parent category.

cif_mag.dic

@@ -2227,7 +2227,7 @@ save_ATOM_SITE_FOURIER_WAVE_VECTOR
     structural model. This category is fully defined in the modulated
     structures dictionary.
 ;
-    _name.category_id             MS_GROUP
+    _name.category_id             MAGNETIC
     _name.object_id               ATOM_SITE_FOURIER_WAVE_VECTOR
     _category_key.name            '_atom_site_Fourier_wave_vector.seq_id'