[ImgBot] Optimize images

*Total -- 331.82kb -> 296.93kb (10.51%)

/repo-img/sample-2.png -- 135.83kb -> 119.96kb (11.69%)
/repo-img/sample-3.png -- 195.98kb -> 176.97kb (9.7%)

Signed-off-by: ImgBotApp <[email protected]>

Author: ImgBotApp