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Summary:
While I'm stuck with https://bugs.kde.org/show_bug.cgi?id=420324, I might as well make
the spurious "no network connectivity" message prettier and more standardized by using the
new Kirigami cimponent introduced in D29057.

Depends on D29057

Test Plan:

Reviewers: VDG, Discover Software Store, apol

Reviewed By: Discover Software Store, apol

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D29059