Fix noxfile for python 3.7/3.8

[bschoenmaeckers]

Not sure how this sneaked through.

xref #5898

[codspeed-hq]

Merging this PR will degrade performance by 16.19%

❌ 1 regressed benchmark
✅ 104 untouched benchmarks
⏩ 1 skipped benchmark¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	drop_many_objects	14.7 µs	17.5 µs	-16.19%

---

_{Comparing bschoenmaeckers:fix-ci-noxfile (5fd449d) with main (e8566a9)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[Tpt]

It seems we need to gate pyrefly on 3.8+ in pytests/pyproject.toml. sorry for that

[davidhewitt]

We can just merge #5912 to "fix" 3.7.

The 3.7 / 3.8 test suites don't block merge, a slight kindness to external contributors to not have to deal with ancient Python versions.

[bschoenmaeckers]

Great to see the emscripten failure solve itself.