docs: Document that `no_proxy` needs to be set for `.testing` not just for `oc` use

[cfergeau]

After configuring my cluster with an external proxy, I wanted to run curl -k -I api.crc.testing, but this failed as I had forgotten to add crc.testing to no_proxy first.

Our documentation only says:

To use an existing oc executable on your host machine, export the .testing domain as part of the no_proxy environment variable.

It is not needed only for oc, but for any cluster interaction.

[stale[bot]]

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[jhcook]

It would be great if this were updated as it’s caught me out, and I’ll never get that time back. 👍

[cfergeau]

I attempted to improve this in https://github.com/cfergeau/crc/commit/9695d882bee14200042f09af26182051daf8c4aa but I am having trouble wording it in a way I like:

If you are not using [command]crc oc-env, when interacting with the cluster, export the .testing domain as part of the no_proxy environment variable.