Remove note about config paths

[saimn]

Follow up to #6512, see comments there for the motivation: this paragraph is confusing as it follows another paragraph on the Astropy default config path. And the information given here is not really useful I think.
cc @pllim @bsipocz

[astropy-bot]

Hi there @saimn 👋 - thanks for the pull request! I'm just a friendly 🤖 that checks for issues related to the changelog and making sure that this pull request is milestoned and labelled correctly. This is mainly intended for the maintainers, so if you are not a maintainer you can ignore this, and a maintainer will let you know if any action is required on your part 😃.

Everything looks good from my point of view! 👍

[pllim]

Is it worth replacing it with a less confusing note that XDG_CONFIG_HOME is also used by other software and then give a link to, say, https://wiki.archlinux.org/index.php/XDG_Base_Directory_support (or something more general) for further reading?

[pllim]

And is this XDG_CONFIG_HOME supported under Windows? It is not clear from the documentation.

[saimn]

@pllim - Good point, XDG is a linux thing (the X Desktop Group), but the code handles this independently from the OS.

[saimn]

@pllim - I tried to explain a bit more XDG_CONFIG_HOME, is it better like this ?

[pllim]

This is much better. Thanks, @saimn !

Should let the CIs run though (no [skip ci]) to make sure Sphinx gives no warning.

[pllim]

I thought "must exist" is more grammatically correct but I am not 100% sure.

[saimn]

Ok thanks, I will update this and squash.

[bsipocz]

Passed (except the osx build that I've cancelled), so I'm merging now. Thanks @saimn!