Update documentation about codehash behaviour according to EIP-1052 and EIP-161

[ustas-eth]

Fixes #14794 by adding a warning for the codehash usage.

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[ustas-eth]

Please, see the following issue: #14794

[r0qs]

Thank you very much @ustas-eth, I just have one comment ;)

[r0qs]

Thanks @ustas-eth. Could you please just squash the commits and rebase with the develop branch? :)

[ustas-eth]

@r0qs I did, but I'm not sure if the result is what you expected. I'm not very proficient with git :')

[r0qs]

@r0qs I did, but I'm not sure if the result is what you expected. I'm not very proficient with git :')

haha no problem, I fixed it for you ;)

Thanks a lot for your contribution!

[r0qs]

I'm kinda of approving myself here, so @cameel, please take a look when you have some time ;)