Update TOV star test input file with more stable parameters.

[ncorsobh]

Proposed changes

Updates the TOV star test input file to use isotropic coordinates and to use more appropriate constraint parameters.

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[nilsdeppe]

Thanks for doing these! A few questions/suggestions. Please let me know if you think they are a good idea or not :)

[ncorsobh]

@nilsdeppe I added your suggested comments, I think they're a good idea. Since this is a very small PR I just squashed immediately

[nilsvu]

better move those comments up 1 line, so they comment on the line directly below them, rather than the line above them (that's how I read code at least) :)

[ncorsobh]

@nilsvu Done. I changed the phrasing to make it even more explicit too

[knelli2]

@nilsvu Do you want to take another look at this?