Fix typing issues for typed Scrapy.

[wRAR]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.97%. Comparing base (bbffb57) to head (3b234c0).
Report is 39 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #166      +/-   ##
==========================================
+ Coverage   84.23%   86.97%   +2.74%     
==========================================
  Files          15       15              
  Lines         926      960      +34     
==========================================
+ Hits          780      835      +55     
+ Misses        146      125      -21     

Files with missing lines	Coverage Δ
scrapy_poet/downloadermiddlewares.py	98.59% <100.00%> (+18.26%)	⬆️
scrapy_poet/injection.py	98.80% <100.00%> (+1.05%)	⬆️
scrapy_poet/page_input_providers.py	98.61% <100.00%> (+0.01%)	⬆️
scrapy_poet/spidermiddlewares.py	100.00% <100.00%> (ø)
scrapy_poet/utils/__init__.py	97.82% <100.00%> (+4.34%)	⬆️
scrapy_poet/utils/testing.py	80.51% <ø> (-0.50%)	⬇️

... and 1 file with indirect coverage changes