valadoc: Correctly format background of inline @link's
valadoc: Correctly format background of inline @link's

Tested in Firefox, Chromium and Gnome Web.

Fixes https://gitlab.gnome.org/GNOME/vala/issues/1226

GNOME/vala,frida/vala,frida/vala,frida/vala,GNOME/vala,GNOME/vala,frida/vala,GNOME/vala,frida/vala