Documentation: dev-tools: use literal block instead of code-block

KTAP Specification: Change code-block directives to straightforward
literal blocks since the blocks do not contain code.

Suggested-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Reviewed-by: David Gow <davidgow@google.com>
Link: https://lore.kernel.org/r/20220316202622.324866-3-frowand.list@gmail.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>