* Remove an obsolete style block related to highlighting from _IRCLayout.pcss Initially it has been added with this commit67249e1e9cfor the implementation of IRC layout, but the border declarations for highlighting were removed with this commit3a2aa9d96cto replace the 'border-left' declaration with the 'box-shadow' declaration. Signed-off-by: Suguru Hirahara <luixxiul@users.noreply.github.com>