Change TWISTED_REACTOR in the default template.

[wRAR]

Fixes #5590

[codecov]

Codecov Report

Merging #5679 (75bb516) into master (715c05d) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5679      +/-   ##
==========================================
- Coverage   88.67%   88.64%   -0.03%     
==========================================
  Files         162      162              
  Lines       10966    10975       +9     
  Branches     1796     1796              
==========================================
+ Hits         9724     9729       +5     
- Misses        961      966       +5     
+ Partials      281      280       -1     

Impacted Files	Coverage Δ
scrapy/commands/parse.py	28.19% <0.00%> (+0.25%)	⬆️
scrapy/core/downloader/__init__.py	92.48% <0.00%> (+1.50%)	⬆️