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 85.87%. Comparing base (bbffb57) to head (dede201).
Report is 2 commits behind head on master.

❗ Current head dede201 differs from pull request most recent head 535dd4e

Please upload reports for the commit 535dd4e to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #166      +/-   ##
==========================================
+ Coverage   84.23%   85.87%   +1.63%     
==========================================
  Files          15       14       -1     
  Lines         926      814     -112     
==========================================
- Hits          780      699      -81     
+ Misses        146      115      -31     

Files	Coverage Δ
scrapy_poet/downloadermiddlewares.py	100.00% <100.00%> (+19.67%)	⬆️
scrapy_poet/injection.py	98.54% <100.00%> (+0.79%)	⬆️
scrapy_poet/page_input_providers.py	100.00% <100.00%> (+1.40%)	⬆️
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	77.16% <ø> (-3.85%)	⬇️

... and 4 files with indirect coverage changes