luci-app-opkg: change remove button caption

Add three dots to the first level 'Remove' button caption, because it
leads to a modal dialogue.

Ref: #2775
Signed-off-by: Dirk Brenken <dev@brenken.org>
[split into multiple commits, sync translations]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>