[ImgBot] Optimize images

*Total -- 280.06kb -> 268.97kb (3.96%)

/svgs/langchain-modules.svg -- 147.84kb -> 140.70kb (4.83%)
/svgs/langchain-use-cases.svg -- 132.22kb -> 128.27kb (2.99%)

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

Author: ImgBotApp