Make typing_extensions import conditional on Python version

[smkent]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.37%. Comparing base (1db7e90) to head (6dce674).

Files with missing lines	Patch %	Lines
copier_python/repo.py	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #69      +/-   ##
==========================================
- Coverage   86.12%   85.37%   -0.75%     
==========================================
  Files           4        4              
  Lines         209      212       +3     
  Branches       19       20       +1     
==========================================
+ Hits          180      181       +1     
- Misses         20       21       +1     
- Partials        9       10       +1     

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