scribusUnstable: fix build failure from poppler bump

Poppler was upgraded in [0] and therefore the build broke, as
poppler/goo/gtypes.h was moved into poppler/goo/gfile.h [1].

The patch is intended to be broght upstream and then can be reverted.

[0] https://github.com/NixOS/nixpkgs/commit/7757e43fcb15f3b3e21187787edaad54614ec7e6
[1] https://gitlab.freedesktop.org/poppler/poppler/commit/ef3ef702bc3dc845731e43215400448c5324efd4