Remove deprecated external community doc links

[andrewdavidwong]

See the discussion at: https://forum.qubes-os.org/t/21746/

Companion PR: QubesOS/qubesos.github.io#236

[andrewdavidwong]

I couldn't figure out how to programmatically replace every community GitHub link with a link to https://forum.qubes-os.org/c/guides/14, so I just removed them instead. However, I realized after submitting this PR that this will break all existing links to https://www.qubes-os.org/doc/* that were being redirected to those GitHub pages, so this is definitely not the best way to do things. Hopefully someone more skilled can do a better version of this, and this PR never has to be merged.

[marmarek]

I couldn't figure out how to programmatically replace every community GitHub link with a link to https://forum.qubes-os.org/c/guides/14,

Is it okay to replace all with this very link (to the category, not individual guides)? If so, I can make a PR.

[andrewdavidwong]

Is it okay to replace all with this very link (to the category, not individual guides)? If so, I can make a PR.

That's up to @unman. It was discussed in the linked thread, and the only consensus seems to be that more specific links would be better.

[unman]

It's definitely better to use specific links, and links that will generate "good" search results - that means full titles since they incorporate the likely search terms, rather than short, but working, forum links. The same goes for redirects from the old GitHub community pages - these should redirect automatically to the full titled pages, and also incorporate a text link in case the redirect should fail for some reason..

[marmarek]

A bit better approach here: #1346

[andrewdavidwong]

Closing in favor of #1346.