Merge pull request numpy#21372 from seberg/relax-legacycast-parametric

BUG: Allow legacy dtypes to cast to datetime again

Author: mattip

numpy/core/src/multiarray/convert_datatype.c

@@ -107,9 +107,6 @@ PyArray_GetCastingImpl(PyArray_DTypeMeta *from, PyArray_DTypeMeta *to)
         return NULL;
     }
     else {
-        if (NPY_DT_is_parametric(from) || NPY_DT_is_parametric(to)) {
-            Py_RETURN_NONE;
-        }
         /* Reject non-legacy dtypes (they need to use the new API) */
         if (!NPY_DT_is_legacy(from) || !NPY_DT_is_legacy(to)) {
             Py_RETURN_NONE;