Translate German variable names in Calc (financial)

These names of variables correspond to German function names in Calc
and were translated to their English equivalents. For used translations,
see, e.g., https://translations.documentfoundation.org/de/libo54_help/translate/#search=kapz&sfields=target

Change-Id: I5c0e4232b2e7b3039a42aff96a44a8f55c818d2e
Reviewed-on: https://gerrit.libreoffice.org/42993Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>