BUG: fix LaTeX typesetting for fractional ylabels in LinePlot

[neutrinoceros]

PR Summary

Goal: fix #3636
I'm cargo culting a bit here, so I'll open as a draft.

[neutrinoceros]

The fact that this passed the answer job shows that it's not yet fixing the targeted problem.

[neutrinoceros]

Got the right fix, rebased.

[cphyc]

Happy about the changes if the answers are bumped!

[neutrinoceros]

done in yt-project/answer-store#26

[neutrinoceros]

@matthewturk, @cphyc, any chance you could merge the answer store PR ?

[matthewturk]

merged

[neutrinoceros]

@meeseeksdev backport to yt-4.0.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

$ git checkout yt-4.0.x
$ git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

$ git cherry-pick -m1 60c352456148c62a407a376673092e33d9db03e3

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

$ git commit -am 'Backport PR #3637: BUG: fix LaTeX typesetting for fractional ylabels in LinePlot'

4. Push to a named branch :

git push YOURFORK yt-4.0.x:auto-backport-of-pr-3637-on-yt-4.0.x

5. Create a PR against branch yt-4.0.x, I would have named this PR:

"Backport PR #3637 on branch yt-4.0.x (BUG: fix LaTeX typesetting for fractional ylabels in LinePlot)"

And apply the correct labels and milestones.

Congratulation you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove Still Needs Manual Backport label once the PR gets merged.

If these instruction are inaccurate, feel free to suggest an improvement.

[neutrinoceros]

the conflict for this one is in the answer-store submodule. Most likely we need to merge #3644 first and then we'll be able to backport this one.