Revert "According to the spec the language node's code attribute is 'langcode', not 'languagecode'"

Translation of languagecode -> langcode is done by the "@langcode=languagecode" line later in
the file.

This reverts commit dbe5d0c70de675f75a3f5a40a480f4b57ec9c5fc.
Merge branch 'master' into importer_updates