[ImgBot] Optimize images

*Total -- 382.53kb -> 273.91kb (28.4%)

/Doc/library/kde_example.png -- 307.76kb -> 207.27kb (32.65%)
/Doc/howto/logging_flow.svg -- 13.97kb -> 10.55kb (24.51%)
/Doc/c-api/lifecycle.dot.svg -- 21.28kb -> 18.92kb (11.09%)
/Doc/library/heapq-binary-tree.svg -- 39.52kb -> 37.17kb (5.93%)

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