[FORMATTING] Remove RH references from Che docs

Changes introduced in https://github.com/eclipse/che-docs/pull/1220/files add RH-specific content into upstream.

The problem with using !=che is that it's introducing RH-specific content into upstream. It doesn't get built in upstream, but it's in the code, which is not goopd. What if, for example, some other company wanted to downstream these docs?

I see two possible solutions:

1) Use attributes for the entire URLs. That's pbbly most straightforward but also ugly and would introduce many very specific attributes.

2) Use included snippets. This is more complicated but could work because it would be possible to create a file with all the different URLs (or pieces of content) and then include its specific parts based on anchors. See https://asciidoctor.org/docs/user-manual/#by-tagged-regions

I'm leaning toward #2.