Cleanup deprecated fingerprint code in scrapy.utils.request

[Laerte]

Closes #6212

[codecov]

Codecov Report

Merging #6213 (53ccf00) into master (4229048) will decrease coverage by 0.07%.
The diff coverage is 75.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6213      +/-   ##
==========================================
- Coverage   88.62%   88.55%   -0.07%     
==========================================
  Files         160      160              
  Lines       11638    11607      -31     
  Branches     1892     1883       -9     
==========================================
- Hits        10314    10279      -35     
- Misses        999     1003       +4     
  Partials      325      325              

Files	Coverage Δ
scrapy/settings/default_settings.py	98.80% <100.00%> (ø)
scrapy/utils/test.py	84.81% <ø> (-0.38%)	⬇️
scrapy/utils/request.py	90.09% <66.66%> (-5.29%)	⬇️

[Gallaecio]

My plan here was to deprecate REQUEST_FINGERPRINTER_IMPLEMENTATION itself now, and remove the setting altogether in a year.

[Laerte]

My plan here was to deprecate REQUEST_FINGERPRINTER_IMPLEMENTATION itself now, and remove the setting altogether in a year.

Should i add a deprecation warning to RequestFingerprinter constructor then?

[Gallaecio]

I’m open when it comes to how to implement that, but one way to go about it would be to switch the default to some sentinel value (e.g. "SENTINEL"), and log a deprecation message if the value is something else, asking for the removal of the setting altogether.

And we should stop adding the setting to settings.py when using startproject.

And we can entirely remove any mention of the setting from the docs.