Fix image links

[yinghui-hu]

Current links work on https://quantumai.google/ but not on Colab or GitHub webpage

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[pavoljuhas]

Please replace (here and below) with a relative link, e.g., (../images/CircuitMomentOperation.png)

[yinghui-hu]

Done

[pavoljuhas]

Thank you @yinghui-hu for your suggestion.

The https://quantumai.google website already has these files under the cirq/images path.
It is preferable to use those rather than external files from github.com which may be less optimal for serving static files.

The relative paths of images under https://quantumai.google/cirq/... and https://github.com/quantumlib/Cirq/tree/master/docs/... are the same,
so both cases on GitHub and web can be satisfied by using relative paths.

[yinghui-hu]

Thank you @yinghui-hu for your suggestion.

The https://quantumai.google website already has these files under the cirq/images path. It is preferable to use those rather than external files from github.com which may be less optimal for serving static files.

The relative paths of images under https://quantumai.google/cirq/... and https://github.com/quantumlib/Cirq/tree/master/docs/... are the same, so both cases on GitHub and web can be satisfied by using relative paths.

Done

[pavoljuhas]

LGTM, thank you!

[yinghui-hu]

Thanks for the review, Pavol!