Both sentences seem to me are with same meaning that the job is finished .
But, I think grammatically there is difference that ( Sentence in the past tense ) means that the job is done but with no exact time in the past . When (2nd Sentence should be " the job has been doing" which is present perfect continuous that means the job was doing untill is finished now .
Both sentences are proper english.If you say "The job is done" I would understand that you did it yourself or you took part in the process
....in the other sentence "the job has been done", I would understand that somebody else "took care of the job " either for you or irrespective of whether you took part in the job or not....