[KdePlasma-Addons/POTD/NOAA] Fixed the web address and fetched the picture from new address

Summary:
The web address for NOAA is no longer valid. So, the new address had to be provided.

Old address: http://www.nnvl.noaa.gov/imageoftheday.php
new address: https://www.nesdis.noaa.gov/content/imagery-and-data

'Image of the day' has a new landing page everyday. So the code had to slightly altered to fetch image from new address.

Test Plan: All plugins should work as usual.

Reviewers: Plasma, kossebau, davidedmundson

Reviewed By: Plasma, davidedmundson

Subscribers: ngraham, plasma-devel, Plasma

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D13868