asciidoctor: Fix giteveryday.txt to be built with asciidoctor.

When building the `doc` with `asciidoctor`, `asciidoctor` complains about
a nested code block in a callout list. This is a really dirty solution to
restore the callout list to function properly. There is a minimal visual
sideeffect; the *immitated* codeblock has no overall greyish background.
Instead the individual lines have it.

Note: When building this patch with `asciidoc` the background is totally
gone but the font is still monospaced.

Signed-off-by: nalla <[email protected]>

Author: nalla