Bug 27661: Update about for message broker status

Bug 27661: Update about for message broker status

This patch updates the about page with regards to the message broker
status and adds some small formatting improvements for displaying the
status.

Test plan
1/ Run through the yarn build process to update the CSS file.
2/ View the about page without RabbitMQ installed
3/ View the about page with RabbitMQ installed
4/ Note the formatting and message change and signoff

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>