po: Remove English strings from the Polish translation.

[Jacek Caban]

Hi Francois,

On 07/20/11 16:14, Francois Gouget wrote:
> ---
>  po/pl.po |   88 +++++++++++++++++++++++++++++++-------------------------------
>  1 files changed, 44 insertions(+), 44 deletions(-)
>

Separator, diagram and folder are the right Polish translations (that
happen to be identical to English). Others should, obviously, be removed.

Jacek