Fix auth in aboutjson

[hugobuddel]

Closes #3991

This uses the Channel class from conda to sanitize the channel url, instead of relying on a regular expression.

This does mean that the channel format in about.json now is different. E.g. see these test urls:

https://conda.anaconda.org/t/ms-534991f2-4123-473a-b512-42025291b927/somechannel
https://myuser:mypass@conda.anaconda.org/somechannel

Previously these would become

https://conda.anaconda.org/t/<TOKEN>/somechannel
https://myuser:mypass@conda.anaconda.org/somechannel

Now they are both

https://conda.anaconda.org/somechannel
https://conda.anaconda.org/somechannel

This is better, because

• it is standardized with how conda itself does things
• it should not matter how the channel is authenticated.

[Edit: removed something about clahub.com being down; apparently I signed the CLA already in the past]

[mingwandroid]

Thanks!

[github-actions]

Hi there, thank you for your contribution!

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Please open a new issue or pull request if needed.

Thanks!