Make the "unsupported input JPEG file" message correct.
Make the "unsupported input JPEG file" message correct.

This pertains to #40

guanzidashu/guetzli_ios_metal,ianhuang-777/guetzli,ianhuang-777/guetzli,dloeng/guetzli,ianhuang-777/guetzli,dloeng/guetzli,guanzidashu/guetzli_ios_metal,dloeng/guetzli,google/guetzli,ianhuang-777/guetzli,google/guetzli,guanzidashu/guetzli_ios_metal,szabadka/guetzli,google/guetzli,guanzidashu/guetzli_ios_metal,google/guetzli,szabadka/guetzli,szabadka/guetzli