Fix links style in Talk sidebar in public share auth page
Fix links style in Talk sidebar in public share auth page

"guest.css" overrides the default style of links set in "style.scss"
(core), which causes links in the public share auth page to be white and
with a stronger weight. Due to this, the rules from "style.scss" need to
be restored for links in the Talk sidebar to get the proper appearance.

Note that, unlike in other restored rules, in this case it is not enough
to use "#talk-sidebar" as the main selector; "#body-login #talk-sidebar"
needs to be used in this case.

Signed-off-by: Daniel Calviño Sánchez <bd7629e975cc0e00ea7cda4ab6a120f2ee42ac1b@gmail.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed