docs: fix invalid rst syntax

We need a newline here to avoid syntax errors while builind the
sphinx-documentation.

The errors don't lead the build fail, so we didn't notice this on CI.
Which is a shame IMO. Instead, the blocks simply fail to render.

Fixes: 2e2edaa89b ("docs/ci: Document setting up the http cache for traces.")
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8839>

docs/ci/bare-metal.rst

@@ -136,6 +136,7 @@ To improve the runtime for downloading traces during traces job runs, you will
 want a pass-through HTTP cache.  On your runner box, install nginx:
 
 .. code-block:: console
+
   sudo apt install nginx libnginx-mod-http-lua
 
 Add the server setup files:
@@ -152,6 +153,7 @@ your devices are on.
 Enable the site and restart nginx:
 
 .. code-block:: console
+
   sudo ln -s /etc/nginx/sites-available/fdo-cache /etc/nginx/sites-enabled/fdo-cache
   sudo service nginx restart