refactor(http): align additional error messages

[irbull]

Aligns the error messages in the http folder to match the style guide.

https://github.com/denoland/std/issues/5574

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.22%. Comparing base (c817a5a) to head (8556b75). Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5791      +/-   ##
==========================================
- Coverage   96.23%   96.22%   -0.02%     
==========================================
  Files         480      480              
  Lines       38748    38759      +11     
  Branches     5616     5616              
==========================================
+ Hits        37291    37295       +4     
- Misses       1416     1423       +7     
  Partials       41       41              

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