Sort keys in json encoder

Summary:
Should supress scripty noise.

The previous manualy sorting above was ultimately useless as it's stored
as a map internally inside the json blob. We need to sort when writing out,
it turns out there's an argument for that.

Test Plan:
Ran script
Still got some output.
Running twice didn't change output

Reviewers: Plasma

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D15793