Fixes stray references to run.py

[DrPaulSharp]

Description

The test file run_one.py contains a reference to the now-removed file run.py. This PR updates it to __main__.py.

How Has This Been Tested?

Tested that the file correctly runs a single test file.

Review Checklist:

[if using the editor, use [x] in place of [ ] to check a box]

Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)
  • Wheels installer (GH artifact) has been tested (installed and worked)

Licensing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)

[jellybean2004]

All good.

[llimeht]

My thinking was that this file should just go (along with some others). Our test runner is pytest not unittest, so who knows whether this even works in general

(I had put it in my collection of nitpicks to deal with one day)

[DrPaulSharp]

My thinking was that this file should just go (along with some others). Our test runner is pytest not unittest, so who knows whether this even works in general

(I had put it in my collection of nitpicks to deal with one day)

Yeah, that makes sense to me. This just makes the file work without crashing for now, but I see no reason to retain it long term.