Reduce requirements

[cthoyt]

Make requests and click optional requirements

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 75.56%. Comparing base (1ca7fa5) to head (ca179e0).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pystow/utils/download.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
- Coverage   75.57%   75.56%   -0.02%     
==========================================
  Files          17       17              
  Lines        1736     1739       +3     
  Branches      204      204              
==========================================
+ Hits         1312     1314       +2     
- Misses        334      335       +1     
  Partials       90       90              

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