MAINT: Remove __futre__

[Zeroto521]

• closes https://docs.python.org/3/whatsnew/3.9.html#type-hinting-generics-in-standard-collections
• whatsnew entry

Python 3.9 natively supports list.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (aa7440b) 99.30% compared to head (5fe24f1) 99.55%.
Report is 3 commits behind head on main.

❗ Current head 5fe24f1 differs from pull request most recent head 2061c71. Consider uploading reports for the commit 2061c71 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #572      +/-   ##
==========================================
+ Coverage   99.30%   99.55%   +0.25%     
==========================================
  Files         154       78      -76     
  Lines        2292      903    -1389     
  Branches      497      101     -396     
==========================================
- Hits         2276      899    -1377     
+ Misses          7        1       -6     
+ Partials        9        3       -6     

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