Make workspaces produced by GetNegMuMuonicXRD plottable

[MattKing06]

The x-values featured in the dictionary for the GetNegMuMuonicXRD algorithm needed to be sorted in ascending order so that they could be plotted.

To Test:

• Load GetNegMuMuonicXRD
• Choose any element
• select a value for Y-shift
• enter a name for the output workspace
• Run the algorithm
• Right click -> Plot Spectrum for each workspace in the output group workspace
• See that they actually plot

Release Notes: //todo

Fixes #14347

[ElliotAOram]

This works as described. I'm happy to merge once is passes the build servers
@MattKing06 Two things for possible future development (Not sure if this is appropriate - please ignore if not!)

1. It would be nice to see something in the Sample Log. Currently it only contains run_title.
2. Secondly it might be worth populating the Sample Material with at the least the Formula
   These could be separate issues as they are unrelated to this issue

[MattKing06]

@ElliotAOram I think you're right, I will discuss was could be contained in the sample logs with Adrian when I next see him. Thanks! 👍