since the gsf dependency has gone, remove it from the .pc file too
since the gsf dependency has gone, remove it from the .pc file too

Distrotech/librevenge,cpjreynolds/libwpd,Distrotech/librevenge,cpjreynolds/libwpd,Distrotech/librevenge,Distrotech/libpwd,Distrotech/libpwd,Distrotech/librevenge,Distrotech/libpwd,Distrotech/libpwd,Distrotech/librevenge,cpjreynolds/libwpd