luci-theme-bootstrap: update href for Bootstrap "brand"

In the Material theme, clicking on the logo takes you to the status page.
This seems logical, and is very helpful. But in Bootstrap, it doesn't
do anything, so just pulling the same href from Material to Bootstrap,
so the link works in Bootstrap as well.

Signed-off-by: Russell Morris <rmorris@rkmorris.us>
[adjust commit subject, squash commits]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>