docs(README): correct the example code for the consumption of respons…

[tenkirin]

This relates to...

Docs, fix #4657

Changes

Simply removed the unnecessary res.

- await res.body.dump(); // force consumption of body
+ await body.dump(); // force consumption of body

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.86%. Comparing base (9271564) to head (4212e6c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4658      +/-   ##
==========================================
+ Coverage   92.84%   92.86%   +0.01%     
==========================================
  Files         106      106              
  Lines       33272    33272              
==========================================
+ Hits        30892    30897       +5     
+ Misses       2380     2375       -5     

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