Fix Spanish translation of "Open folders in new tabs on middle click"

I would create a PR but I just created an account here and I'm not allowed to fork the repo.

Open folders in new tabs on middle click is mistranslated, it should be "Abrir las carpetas en pestañas nuevas con el clic central" (it currently says "windows" instead of "tabs").

Also, this is not an error but it's inconsistent: Are you sure that you want to permanently delete the selected file? can follow the pattern of the plural version: "¿Seguro que quiere eliminar permanentemente\nel archivo seleccionado?"