[ImgBot] Optimize images

*Total -- 3,884.08kb -> 3,036.49kb (21.82%)

/images/Undirected.jpg -- 850.41kb -> 593.32kb (30.23%)
/images/Business Problem Framework.png -- 175.58kb -> 126.18kb (28.14%)
/images/Pruning and Threshold.jpg -- 954.13kb -> 703.20kb (26.3%)
/images/Nodes and Edges.jpg -- 887.90kb -> 654.49kb (26.29%)
/images/ml6.jpg -- 360.30kb -> 305.78kb (15.13%)
/images/Customer Segmentation Workflow.png -- 655.75kb -> 653.51kb (0.34%)

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

Author: ImgBotApp