[ImgBot] Optimize images

*Total -- 324.20kb -> 314.77kb (2.91%)

/img/sponsors-img/dev.png -- 16.02kb -> 8.94kb (44.19%)
/img/sponsors-img/unnathiIBM.png -- 308.18kb -> 305.82kb (0.76%)

Signed-off-by: ImgBotApp <ImgBotHelp@gmail.com>

Author: ImgBotApp