[mobile/wifi] Remove broken confirmation dialog when forgetting a connection

Summary: The confirmation is broken and doesn't appear at all. IMHO it isn't really necessary, so let's remove it.

Test Plan: Deleted a connection

Reviewers: Plasma, jgrulich

Reviewed By: jgrulich

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D24897