More docs for the is_asyncio_reactor_installed() behavior change.

[wRAR]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.83%. Comparing base (b20995c) to head (31aefd2).
Report is 2 commits behind head on 2.13.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
scrapy/utils/test.py	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             2.13    #6866      +/-   ##
==========================================
- Coverage   90.85%   90.83%   -0.02%     
==========================================
  Files         164      164              
  Lines       12353    12355       +2     
  Branches     1606     1607       +1     
==========================================
  Hits        11223    11223              
- Misses        828      829       +1     
- Partials      302      303       +1     

Files with missing lines	Coverage Δ
scrapy/utils/reactor.py	88.88% <ø> (ø)
scrapy/utils/test.py	55.31% <33.33%> (-1.21%)	⬇️

[wRAR]

Writing a test for this would need running a standalone script, but I checked this with scrapinghub-entrypoint-scrapy before scrapinghub/scrapinghub-entrypoint-scrapy#94 and it produces the correct exception.