dev-python/mpxj: add pypi upstream metadata

Signed-off-by: Lucio Sauer <[email protected]>

Author: antecrescent

dev-python/mpxj/metadata.xml

@@ -7,5 +7,6 @@
         </maintainer>
         <upstream>
                 <remote-id type="github">joniles/mpxj</remote-id>
+                <remote-id type="pypi">mpxj</remote-id>
         </upstream>
 </pkgmetadata>