Fix bug where edge colors are randomly shuffled in mpl_draw (backport #1312)

[mergify]

Closes #1308. A bit embarrasing but we let that slip through in #1204.

The solution is a bit hacky but reusing Python dictionaries was the easiest way to get a set-like object that preservers iteration order.

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This is an automatic backport of pull request #1312 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 44d9fb0 has failed:

On branch mergify/bp/stable/0.14/pr-1312
Your branch is up to date with 'origin/stable/0.14'.

You are currently cherry-picking commit 44d9fb0.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   releasenotes/notes/correct-edge-colors-e082e1761e1c060b.yaml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   rustworkx/visualization/matplotlib.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[IvanIsCoding]

I think we are going to release 0.16. not 0.15.2. If that changes I will reopen