[ImgBot] Optimize images (#133)

*Total -- 151.00kb -> 133.25kb (11.75%)

/Guides/Resources/SortedPrefix/FewElements.png -- 73.60kb -> 64.27kb (12.67%)
/Guides/Resources/SortedPrefix/ManyElements.png -- 77.40kb -> 68.98kb (10.87%)

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

Co-authored-by: ImgBotApp <ImgBotHelp@gmail.com>

Author: LemonSpike