更新 figure-MT-system-as-a-black-box.tex

Book/Chapter2/Figures/figure-MT-system-as-a-black-box.tex → Book/Chapter2/Figures/figure-mt-system-as-a-black-box.tex

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 \definecolor{ublue}{rgb}{0.152,0.250,0.545}
 \definecolor{ugreen}{rgb}{0,0.5,0}