fix: avoid broken rustworkx version for Python 3.7

[mrossinek]

Summary

Details and comments

[mrossinek]

Since rustworkx is only an indirect dependency, I suppose this needs to be fixed on Nature directly rather than here. I am leaving this open for now but will likely close it in favor of a PR over there :+1:

[mrossinek]

Since https://github.com/qiskit-community/qiskit-nature/pull/1202 seems to not have propagated down to this repo, in this PR I am now switching to install Nature from stable instead of main. Hopefully together with the constraint added for this repo this will fix things.

[coveralls]

Pull Request Test Coverage Report for Build 5212525674

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 69.697%

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Totals
Change from base Build 5070533279:	0.0%
Covered Lines:	69
Relevant Lines:	99

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💛 - Coveralls