fix a regression from de-autoboxing  transformer

The upgrade_nonpod method is supposed to replace the referenced
array's content in place, but instead a new reference was built
and then thrown away.
add test for regression fixed in previous commit
v0.103004

        - fix a regression in 0.103003, in which Nonpod paragraphs were not
          converted into Pod5::Nonpod paragraphs by the Pod5 transformer