Documentation: net: net_failover: Separate cloud-ifupdown-helper and reattach-vf...

Documentation: net: net_failover: Separate cloud-ifupdown-helper and reattach-vf.sh code blocks marker

cloud-ifupdown-helper patch and reattach-vf.sh script are rendered in
htmldocs output as normal paragraphs instead of literal code blocks
due to missing separator from respective code block marker. Add it.

Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20251016093936.29442-2-bagasdotme@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>