If your /etc/cups/mime.convs contains manual changes which you do not want to sacrifice, please remove the line(s) with "pstoraster" or replace all occurrences of "pstoraster" by "gstoraster", after that restart CUPS ("sudo restart cups" in a terminal window). If you never edited /etc/cups/mime.convs and do not have any proprietary printer drivers which could have modified this file, remove the file and then restart CUPS. Then your problem should disappear.
If your /etc/cups/ mime.convs contains manual changes which you do not want to sacrifice, please remove the line(s) with "pstoraster" or replace all occurrences of "pstoraster" by "gstoraster", after that restart CUPS ("sudo restart cups" in a terminal window). If you never edited /etc/cups/ mime.convs and do not have any proprietary printer drivers which could have modified this file, remove the file and then restart CUPS. Then your problem should disappear.