[KdePlasma-Addons/POTD/EOPD] Fixed RegEx string to accommodate both HTTP/HTTPS protocols

Summary: This provider currently fails over HTTPS connection. This patch fixes the RegEx string to accommodate both HTTP/HTTPS protocols.

Test Plan: All plugins should work as usual.

Reviewers: davidedmundson, ngraham

Subscribers: ngraham, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D18451