Community Site: Clean up fetch_docs to remove asciidoc warnings

fetch_docs.rb generates html for .adoc files which results in warnings when building the community site, such as the following:

asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: topics
asciidoctor: WARNING: dropping line containing reference to missing attribute: stories
asciidoctor: WARNING: dropping line containing reference to missing attribute: stories
asciidoctor: WARNING: dropping line containing reference to missing attribute: stories
asciidoctor: WARNING: dropping line containing reference to missing attribute: stories
asciidoctor: WARNING: dropping line containing reference to missing attribute: stories
asciidoctor: WARNING: oc_logs_clusterview.adoc: line 7: invalid style for paragraph:

{example_crd_name}-0|0] (1) [{example_crd_name}

-0

The purpose of this task is to modify fetch_docs.rb so that it generates HTML from the .asciidoc file only. Also leave the community site in a cleaner state. No need to copy across the asciidoc files and other content. We only need a single HTML file per title on the site.