[ImgBot] Optimize images

*Total -- 2,131.21kb -> 1,519.07kb (28.72%)

/src/img/wpa-stack.png -- 142.16kb -> 74.95kb (47.28%)
/src/img/coverage-branch-counting-01.png -- 11.02kb -> 6.11kb (44.58%)
/src/img/llvm-cov-show-01.png -- 406.98kb -> 242.59kb (40.39%)
/src/queries/example-0.png -- 104.08kb -> 65.67kb (36.9%)
/src/img/github-cli.png -- 26.16kb -> 17.17kb (34.36%)
/src/img/submodule-conflicts.png -- 19.74kb -> 13.10kb (33.63%)
/src/img/dataflow-graphviz-example.png -- 79.97kb -> 53.10kb (33.6%)
/src/img/coverage-graphviz-01.png -- 332.43kb -> 226.35kb (31.91%)
/src/img/rustbot-submodules.png -- 25.42kb -> 17.63kb (30.64%)
/src/img/other-peoples-commits.png -- 294.45kb -> 216.95kb (26.32%)
/src/img/github-whitespace-changes.png -- 28.53kb -> 21.22kb (25.64%)
/src/mir/mir_overview.svg -- 5.20kb -> 4.23kb (18.64%)
/src/img/coverage-spanview-01.png -- 313.14kb -> 255.07kb (18.55%)
/src/mir/mir_detailed.svg -- 17.49kb -> 14.67kb (16.12%)
/src/img/wpa-initial-memory.png -- 305.31kb -> 272.61kb (10.71%)
/src/mir/mir_cfg.svg -- 19.13kb -> 17.63kb (7.8%)

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

Author: ImgBotApp