Fix style of commit-filter links in commit-subject.

When using the commit-filter functionality to add e.g. bug tracker links to
commit messages, the style of those links is mangled by a CSS directive that
is meant to only apply to decorations that are listed on the commit-subject
line.

Fix this directive to only apply to the decorations.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>