Only even try to import stdlib-list if we're less than py39

[ericdill]

@mariusvniekerk ran into an issue where stdlib-list was in the environment but python was >=3.10. so he was getting the stdlib-list import attempt even though we use a different code path for 3.10. this PR fixes that by making the version checking stricter.

[codecov-commenter]

Codecov Report

Base: 92.54% // Head: 91.75% // Decreases project coverage by -0.78% ⚠️

Coverage data is based on head (c72ad2c) compared to base (e7d8463).
Patch coverage: 72.72% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
- Coverage   92.54%   91.75%   -0.79%     
==========================================
  Files           7        7              
  Lines         456      461       +5     
==========================================
+ Hits          422      423       +1     
- Misses         34       38       +4     

Impacted Files	Coverage Δ
depfinder/stdliblist.py	69.23% <72.72%> (-30.77%)	⬇️

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