bpo-30660: Replaced PNG files with their lossless optimized version

[tiagofilipesilva]

https://bugs.python.org/issue30660

[the-knights-who-say-ni]

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[tiagofilipesilva]

Sorry everybody, first time using GitHub.

CLA signed; can't add a "trivial" tag.

[serhiy-storchaka]

Why these changes are needed? This isn't a trivial issue, it need to be discussed on the bug tracker.

[rhettinger]

This new PNGs look fine to me. How much space is saved?

[tiagofilipesilva]

Sorry Raymond, I had to deal with some things and simply wasn't around…
If I recall properly, ≈ 5 to 50 % depending on the file.

[methane]

I want reproducible compression step.