[ImgBot] Optimize images

*Total -- 516.89kb -> 463.15kb (10.4%)

/Cryptography/morse_code/cyb_morse.png -- 73.70kb -> 59.79kb (18.87%)
/Forensics/binwalk/cchef.png -- 202.31kb -> 165.92kb (17.99%)
/Misc/qr_code/cobang_ss.png -- 48.92kb -> 48.07kb (1.74%)
/Forensics/rubber_duck/RubberDuck.jpg -- 191.96kb -> 189.37kb (1.35%)

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